diff --git a/pyproject.toml b/pyproject.toml
index 13a684dd3..649bedeeb 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -122,6 +122,7 @@ addopts = [
   "-rf",
   "-vv",
 ]
+asyncio_default_fixture_loop_scope = "function"
 doctest_optionflags = [
   "ELLIPSIS"
 ]
diff --git a/supriya/contexts/__init__.py b/supriya/contexts/__init__.py
index 2ece96390..8a0232a84 100644
--- a/supriya/contexts/__init__.py
+++ b/supriya/contexts/__init__.py
@@ -14,7 +14,7 @@
     Synth,
 )
 from .nonrealtime import Score
-from .realtime import AsyncServer, BaseServer, Server
+from .realtime import AsyncServer, BaseServer, Server, ServerLifecycleEvent
 
 __all__ = [
     "AsyncServer",
@@ -29,5 +29,6 @@
     "Node",
     "Score",
     "Server",
+    "ServerLifecycleEvent",
     "Synth",
 ]
diff --git a/supriya/contexts/entities.py b/supriya/contexts/entities.py
index 26d479add..b0ade53ef 100644
--- a/supriya/contexts/entities.py
+++ b/supriya/contexts/entities.py
@@ -568,6 +568,21 @@ def free(self):
         """
         self.context.free_bus_group(self)
 
+    def get(
+        self, sync: bool = True
+    ) -> Union[Awaitable[Optional[Sequence[float]]], Optional[Sequence[float]]]:
+        """
+        Get the control bus group's values.
+
+        Emit ``/c_getn`` requests.
+
+        :param sync: If true, communicate the request immediately. Otherwise bundle it
+            with the current request context.
+        """
+        return cast(Union["AsyncServer", "Server"], self.context).get_bus_range(
+            bus=self[0], count=len(self), sync=sync
+        )
+
     def map_symbol(self) -> str:
         """
         Get the bus group's map symbol.
@@ -578,6 +593,22 @@ def map_symbol(self) -> str:
             return f"c{self.id_}"
         raise InvalidCalculationRate
 
+    def set(self, values: Union[float, Sequence[float]]) -> None:
+        """
+        Set a range of control buses.
+
+        Emit ``/c_setn`` or ``/c_fill`` requests.
+
+        :param values: The values to write. If a float is passed, use that as a fill.
+        """
+        if isinstance(values, float):
+            if len(self) == 1:
+                self.context.set_bus(bus=self[0], value=values)
+            else:
+                self.context.fill_bus_range(bus=self[0], count=len(self), value=values)
+        else:
+            self.context.set_bus_range(bus=self[0], values=values)
+
 
 @dataclasses.dataclass(frozen=True)
 class Node(ContextObject):
diff --git a/supriya/contexts/realtime.py b/supriya/contexts/realtime.py
index 923e62f36..5e6080c77 100644
--- a/supriya/contexts/realtime.py
+++ b/supriya/contexts/realtime.py
@@ -11,7 +11,9 @@
 from collections.abc import Sequence as SequenceABC
 from typing import (
     TYPE_CHECKING,
+    Any,
     Callable,
+    Coroutine,
     Dict,
     Iterable,
     List,
@@ -357,7 +359,7 @@ def _validate_moment_timestamp(self, seconds: Optional[float]) -> None:
     def on(
         self,
         event: Union[ServerLifecycleEvent, Iterable[ServerLifecycleEvent]],
-        callback: Callable[[ServerLifecycleEvent], None],
+        callback: Callable[[ServerLifecycleEvent], Optional[Coroutine[Any, Any, None]]],
     ) -> None:
         if isinstance(event, ServerLifecycleEvent):
             events_ = [event]
@@ -554,6 +556,9 @@ def _lifecycle(self, owned=True) -> None:
 
     def _on_lifecycle_event(self, event: ServerLifecycleEvent) -> None:
         for callback in self._lifecycle_event_callbacks.get(event, []):
+            logger.info(
+                self._log_prefix() + f"lifecycle event: {event.name} {callback}"
+            )
             callback(event)
 
     def _setup_notifications(self) -> None:
@@ -1105,6 +1110,9 @@ async def _lifecycle(self, owned=True) -> None:
 
     async def _on_lifecycle_event(self, event: ServerLifecycleEvent) -> None:
         for callback in self._lifecycle_event_callbacks.get(event, []):
+            logger.info(
+                self._log_prefix() + f"lifecycle event: {event.name} {callback}"
+            )
             if asyncio.iscoroutine(result := callback(event)):
                 await result
 
diff --git a/supriya/contexts/responses.py b/supriya/contexts/responses.py
index 62a434fb0..bf4e3df81 100644
--- a/supriya/contexts/responses.py
+++ b/supriya/contexts/responses.py
@@ -466,8 +466,10 @@ def from_string(cls, string) -> "QueryTreeGroup":
         node_pattern = re.compile(r"^\s*(\d+) (\S+)$")
         control_pattern = re.compile(r"\w+: \S+")
         lines = string.splitlines()
-        if not lines[0].startswith("NODE TREE"):
-            raise ValueError
+        while not lines[0].startswith("NODE TREE"):
+            lines.pop(0)
+        if not lines:
+            raise ValueError(string)
         stack: List[QueryTreeGroup] = [
             QueryTreeGroup(node_id=int(lines.pop(0).rpartition(" ")[-1]))
         ]
diff --git a/supriya/mixers/__init__.py b/supriya/mixers/__init__.py
new file mode 100644
index 000000000..8def09c49
--- /dev/null
+++ b/supriya/mixers/__init__.py
@@ -0,0 +1,3 @@
+from .sessions import Session
+
+__all__ = ["Session"]
diff --git a/supriya/mixers/components.py b/supriya/mixers/components.py
new file mode 100644
index 000000000..f18e5322f
--- /dev/null
+++ b/supriya/mixers/components.py
@@ -0,0 +1,324 @@
+import asyncio
+from typing import (
+    TYPE_CHECKING,
+    Awaitable,
+    Dict,
+    Generator,
+    Generic,
+    Iterator,
+    List,
+    Literal,
+    Optional,
+    Set,
+    Tuple,
+    Type,
+    TypeVar,
+    cast,
+)
+
+try:
+    from typing import TypeAlias
+except ImportError:
+    from typing_extensions import TypeAlias  # noqa
+
+from ..contexts import AsyncServer, Buffer, BusGroup, Context, Group, Node
+from ..contexts.responses import QueryTreeGroup
+from ..enums import BootStatus, CalculationRate
+from ..ugens import SynthDef
+from ..utils import iterate_nwise
+
+C = TypeVar("C", bound="Component")
+
+A = TypeVar("A", bound="AllocatableComponent")
+
+# TODO: Integrate this with channel logic
+ChannelCount: TypeAlias = Literal[1, 2, 4, 8]
+
+if TYPE_CHECKING:
+    from .mixers import Mixer
+    from .sessions import Session
+
+
+class ComponentNames:
+    ACTIVE = "active"
+    CHANNEL_STRIP = "channel-strip"
+    DEVICES = "devices"
+    FEEDBACK = "feedback"
+    GAIN = "gain"
+    GROUP = "group"
+    INPUT = "input"
+    INPUT_LEVELS = "input-levels"
+    MAIN = "main"
+    OUTPUT = "output"
+    OUTPUT_LEVELS = "output-levels"
+    SYNTH = "synth"
+    TRACKS = "tracks"
+
+
+class Component(Generic[C]):
+
+    def __init__(
+        self,
+        *,
+        parent: Optional[C] = None,
+    ) -> None:
+        self._lock = asyncio.Lock()
+        self._parent: Optional[C] = parent
+        self._dependents: Set[Component] = set()
+        self._feedback_dependents: Set[Component] = set()
+
+    def __repr__(self) -> str:
+        return f"<{type(self).__name__}>"
+
+    def _activate(self) -> None:
+        self._is_active = True
+
+    async def _allocate_deep(self, *, context: AsyncServer) -> None:
+        if self.session is None:
+            raise RuntimeError
+        fifo: List[Tuple[Component, int]] = []
+        current_synthdefs = self.session._synthdefs[context]
+        desired_synthdefs: Set[SynthDef] = set()
+        for component in self._walk():
+            fifo.append((component, 0))
+            desired_synthdefs.update(component._get_synthdefs())
+        if required_synthdefs := sorted(
+            desired_synthdefs - current_synthdefs, key=lambda x: x.effective_name
+        ):
+            for synthdef in required_synthdefs:
+                context.add_synthdefs(synthdef)
+            await context.sync()
+            current_synthdefs.update(required_synthdefs)
+        while fifo:
+            component, attempts = fifo.pop(0)
+            if attempts > 2:
+                raise RuntimeError(component, attempts)
+            if not component._allocate(context=context):
+                fifo.append((component, attempts + 1))
+
+    def _allocate(self, *, context: AsyncServer) -> bool:
+        return True
+
+    def _deallocate(self) -> None:
+        pass
+
+    def _deallocate_deep(self) -> None:
+        for component in self._walk():
+            component._deallocate()
+
+    def _deactivate(self) -> None:
+        self._is_active = False
+
+    def _delete(self) -> None:
+        self._deallocate_deep()
+        self._parent = None
+
+    def _get_synthdefs(self) -> List[SynthDef]:
+        return []
+
+    def _iterate_parentage(self) -> Iterator["Component"]:
+        component = self
+        while component.parent is not None:
+            yield component
+            component = component.parent
+        yield component
+
+    def _reconcile(self, context: Optional[AsyncServer] = None) -> bool:
+        return True
+
+    def _register_dependency(self, dependent: "Component") -> None:
+        self._dependents.add(dependent)
+
+    def _register_feedback(
+        self, context: Optional[AsyncServer], dependent: "Component"
+    ) -> Optional[BusGroup]:
+        self._dependents.add(dependent)
+        self._feedback_dependents.add(dependent)
+        return None
+
+    def _unregister_dependency(self, dependent: "Component") -> bool:
+        self._dependents.discard(dependent)
+        return self._unregister_feedback(dependent)
+
+    def _unregister_feedback(self, dependent: "Component") -> bool:
+        had_feedback = bool(self._feedback_dependents)
+        self._feedback_dependents.discard(dependent)
+        return had_feedback and not self._feedback_dependents
+
+    def _walk(
+        self, component_class: Optional[Type["Component"]] = None
+    ) -> Generator["Component", None, None]:
+        component_class_ = component_class or Component
+        if isinstance(self, component_class_):
+            yield self
+        for child in self.children:
+            if isinstance(child, component_class_):
+                yield from child._walk(component_class_)
+
+    @property
+    def address(self) -> str:
+        raise NotImplementedError
+
+    @property
+    def children(self) -> List["Component"]:
+        return []
+
+    @property
+    def context(self) -> Optional[AsyncServer]:
+        if (mixer := self.mixer) is not None:
+            return mixer.context
+        return None
+
+    @property
+    def graph_order(self) -> Tuple[int, ...]:
+        # TODO: Cache this
+        graph_order = []
+        for parent, child in iterate_nwise(reversed(list(self._iterate_parentage()))):
+            graph_order.append(parent.children.index(child))
+        return tuple(graph_order)
+
+    @property
+    def mixer(self) -> Optional["Mixer"]:
+        # TODO: Cache this
+        from .mixers import Mixer
+
+        for component in self._iterate_parentage():
+            if isinstance(component, Mixer):
+                return component
+        return None
+
+    @property
+    def parent(self) -> Optional[C]:
+        return self._parent
+
+    @property
+    def parentage(self) -> List["Component"]:
+        # TODO: Cache this
+        return list(self._iterate_parentage())
+
+    @property
+    def session(self) -> Optional["Session"]:
+        # TODO: Cache this
+        from .sessions import Session
+
+        for component in self._iterate_parentage():
+            if isinstance(component, Session):
+                return component
+        return None
+
+
+class AllocatableComponent(Component[C]):
+
+    def __init__(
+        self,
+        *,
+        parent: Optional[C] = None,
+    ) -> None:
+        super().__init__(parent=parent)
+        self._audio_buses: Dict[str, BusGroup] = {}
+        self._buffers: Dict[str, Buffer] = {}
+        self._context: Optional[Context] = None
+        self._control_buses: Dict[str, BusGroup] = {}
+        self._is_active: bool = True
+        self._nodes: Dict[str, Node] = {}
+
+    def _activate(self) -> None:
+        super()._activate()
+        if group := self._nodes.get(ComponentNames.GROUP):
+            group.unpause()
+            group.set(active=1)
+
+    def _can_allocate(self) -> Optional[AsyncServer]:
+        if (
+            context := self.context
+        ) is not None and context.boot_status == BootStatus.ONLINE:
+            return context
+        return None
+
+    def _deactivate(self) -> None:
+        super()._deactivate()
+        if group := self._nodes.get(ComponentNames.GROUP):
+            group.set(active=0)
+
+    def _deallocate(self) -> None:
+        super()._deallocate()
+        for key in tuple(self._audio_buses):
+            self._audio_buses.pop(key).free()
+        for key in tuple(self._control_buses):
+            self._control_buses.pop(key).free()
+        if group := self._nodes.get(ComponentNames.GROUP):
+            if not self._is_active:
+                group.free()
+            else:
+                group.set(gate=0)
+        self._nodes.clear()
+        for key in tuple(self._buffers):
+            self._buffers.pop(key).free()
+
+    def _get_audio_bus(
+        self,
+        context: Optional[AsyncServer],
+        name: str,
+        can_allocate: bool = False,
+        channel_count: int = 2,
+    ) -> BusGroup:
+        return self._get_buses(
+            calculation_rate=CalculationRate.AUDIO,
+            can_allocate=can_allocate,
+            channel_count=channel_count,
+            context=context,
+            name=name,
+        )
+
+    def _get_buses(
+        self,
+        context: Optional[AsyncServer],
+        name: str,
+        *,
+        calculation_rate: CalculationRate,
+        can_allocate: bool = False,
+        channel_count: int = 1,
+    ) -> BusGroup:
+        if calculation_rate == CalculationRate.CONTROL:
+            buses = self._control_buses
+        elif calculation_rate == CalculationRate.AUDIO:
+            buses = self._audio_buses
+        else:
+            raise ValueError(calculation_rate)
+        if (name not in buses) and can_allocate and context:
+            buses[name] = context.add_bus_group(
+                calculation_rate=calculation_rate,
+                count=channel_count,
+            )
+        return buses[name]
+
+    def _get_control_bus(
+        self,
+        context: Optional[AsyncServer],
+        name: str,
+        can_allocate: bool = False,
+        channel_count: int = 1,
+    ) -> BusGroup:
+        return self._get_buses(
+            calculation_rate=CalculationRate.CONTROL,
+            can_allocate=can_allocate,
+            channel_count=channel_count,
+            context=context,
+            name=name,
+        )
+
+    async def dump_tree(self) -> QueryTreeGroup:
+        if self.session and self.session.status != BootStatus.ONLINE:
+            raise RuntimeError
+        annotations: Dict[int, str] = {}
+        tree = await cast(
+            Awaitable[QueryTreeGroup],
+            cast(Group, self._nodes[ComponentNames.GROUP]).dump_tree(),
+        )
+        for component in self._walk():
+            if not isinstance(component, AllocatableComponent):
+                continue
+            address = component.address
+            for name, node in component._nodes.items():
+                annotations[node.id_] = f"{address}:{name}"
+        return tree.annotate(annotations)
diff --git a/supriya/mixers/devices.py b/supriya/mixers/devices.py
new file mode 100644
index 000000000..9e225187b
--- /dev/null
+++ b/supriya/mixers/devices.py
@@ -0,0 +1,62 @@
+from typing import List
+
+from ..contexts import AsyncServer
+from ..enums import AddAction
+from ..ugens import SynthDef
+from .components import AllocatableComponent, C, ComponentNames
+from .synthdefs import DEVICE_DC_TESTER_2
+
+
+class DeviceContainer(AllocatableComponent[C]):
+
+    def __init__(self) -> None:
+        self._devices: List[Device] = []
+
+    def _delete_device(self, device: "Device") -> None:
+        self._devices.remove(device)
+
+    async def add_device(self) -> "Device":
+        async with self._lock:
+            self._devices.append(device := Device(parent=self))
+            if context := self._can_allocate():
+                await device._allocate_deep(context=context)
+            return device
+
+    @property
+    def devices(self) -> List["Device"]:
+        return self._devices[:]
+
+
+class Device(AllocatableComponent):
+
+    def _allocate(self, *, context: AsyncServer) -> bool:
+        if not super()._allocate(context=context):
+            return False
+        elif self.parent is None:
+            raise RuntimeError
+        main_audio_bus = self.parent._get_audio_bus(context, name=ComponentNames.MAIN)
+        target_node = self.parent._nodes[ComponentNames.DEVICES]
+        with context.at():
+            self._nodes[ComponentNames.GROUP] = group = target_node.add_group(
+                add_action=AddAction.ADD_TO_TAIL
+            )
+            self._nodes[ComponentNames.SYNTH] = group.add_synth(
+                add_action=AddAction.ADD_TO_TAIL,
+                bus=main_audio_bus,
+                synthdef=DEVICE_DC_TESTER_2,
+            )
+        return True
+
+    def _get_synthdefs(self) -> List[SynthDef]:
+        return [DEVICE_DC_TESTER_2]
+
+    async def set_active(self, active: bool = True) -> None:
+        async with self._lock:
+            pass
+
+    @property
+    def address(self) -> str:
+        if self.parent is None:
+            return "devices[?]"
+        index = self.parent.devices.index(self)
+        return f"{self.parent.address}.devices[{index}]"
diff --git a/supriya/mixers/mixers.py b/supriya/mixers/mixers.py
new file mode 100644
index 000000000..68e23243e
--- /dev/null
+++ b/supriya/mixers/mixers.py
@@ -0,0 +1,155 @@
+from typing import TYPE_CHECKING, List, Optional, Tuple
+
+from ..contexts import AsyncServer, BusGroup
+from ..enums import AddAction
+from ..typing import DEFAULT, Default
+from ..ugens import SynthDef
+from .components import AllocatableComponent, Component, ComponentNames
+from .devices import DeviceContainer
+from .routing import Connection
+from .synthdefs import CHANNEL_STRIP_2, METERS_2, PATCH_CABLE_2_2
+from .tracks import Track, TrackContainer
+
+if TYPE_CHECKING:
+    from .sessions import Session
+
+
+class MixerOutput(Connection["Mixer", "Mixer", Default]):
+    def __init__(
+        self,
+        *,
+        parent: "Mixer",
+    ) -> None:
+        super().__init__(
+            name="output",
+            parent=parent,
+            source=parent,
+            target=DEFAULT,
+        )
+
+    def _allocate_synth(
+        self,
+        *,
+        context: AsyncServer,
+        parent: AllocatableComponent,
+        new_state: "Connection.State",
+    ) -> None:
+        self._nodes[ComponentNames.SYNTH] = parent._nodes[
+            ComponentNames.GROUP
+        ].add_synth(
+            add_action=AddAction.ADD_TO_TAIL,
+            in_=new_state.source_bus,
+            out=new_state.target_bus,
+            synthdef=PATCH_CABLE_2_2,
+        )
+
+    def _resolve_default_target(
+        self, context: Optional[AsyncServer]
+    ) -> Tuple[Optional[AllocatableComponent], Optional[BusGroup]]:
+        if not context:
+            return None, None
+        return None, context.audio_output_bus_group
+
+
+class Mixer(TrackContainer["Session"], DeviceContainer):
+
+    # TODO: add_device() -> Device
+    # TODO: group_devices(index: int, count: int) -> Rack
+    # TODO: set_channel_count(self, channel_count: ChannelCount) -> None
+    # TODO: set_output(output: int) -> None
+
+    def __init__(self, *, parent: Optional["Session"]) -> None:
+        AllocatableComponent.__init__(self, parent=parent)
+        DeviceContainer.__init__(self)
+        TrackContainer.__init__(self)
+        self._tracks.append(Track(parent=self))
+        self._output = MixerOutput(parent=self)
+
+    def _allocate(self, context: AsyncServer) -> bool:
+        if not super()._allocate(context=context):
+            return False
+        # self._audio_buses["main"] = context.add_bus_group(
+        #     calculation_rate=CalculationRate.AUDIO,
+        #     count=2,
+        # )
+        main_audio_bus = self._get_audio_bus(
+            context, name=ComponentNames.MAIN, can_allocate=True
+        )
+        gain_control_bus = self._get_control_bus(
+            context, name=ComponentNames.GAIN, can_allocate=True
+        )
+        input_levels_control_bus = self._get_control_bus(
+            context,
+            name=ComponentNames.INPUT_LEVELS,
+            can_allocate=True,
+            channel_count=2,
+        )
+        output_levels_control_bus = self._get_control_bus(
+            context,
+            name=ComponentNames.OUTPUT_LEVELS,
+            can_allocate=True,
+            channel_count=2,
+        )
+        target_node = context.default_group
+        with context.at():
+            gain_control_bus.set(0.0)
+            input_levels_control_bus.set(0.0)
+            output_levels_control_bus.set(0.0)
+            self._nodes[ComponentNames.GROUP] = group = target_node.add_group(
+                add_action=AddAction.ADD_TO_TAIL
+            )
+            self._nodes[ComponentNames.TRACKS] = tracks = group.add_group(
+                add_action=AddAction.ADD_TO_HEAD
+            )
+            self._nodes[ComponentNames.DEVICES] = group.add_group(
+                add_action=AddAction.ADD_TO_TAIL
+            )
+            self._nodes[ComponentNames.CHANNEL_STRIP] = channel_strip = group.add_synth(
+                add_action=AddAction.ADD_TO_TAIL,
+                bus=main_audio_bus,
+                gain=gain_control_bus.map_symbol(),
+                synthdef=CHANNEL_STRIP_2,
+            )
+            self._nodes[ComponentNames.INPUT_LEVELS] = tracks.add_synth(
+                add_action=AddAction.ADD_AFTER,
+                synthdef=METERS_2,
+                in_=self._audio_buses[ComponentNames.MAIN],
+                out=input_levels_control_bus,
+            )
+            self._nodes[ComponentNames.OUTPUT_LEVELS] = channel_strip.add_synth(
+                add_action=AddAction.ADD_AFTER,
+                synthdef=METERS_2,
+                in_=self._audio_buses[ComponentNames.MAIN],
+                out=output_levels_control_bus,
+            )
+        return True
+
+    def _get_synthdefs(self) -> List[SynthDef]:
+        return [
+            CHANNEL_STRIP_2,
+            METERS_2,
+        ]
+
+    async def delete(self) -> None:
+        # TODO: What are delete semantics actually?
+        async with self._lock:
+            if self.session is not None:
+                self.session._delete_mixer(self)
+            self._delete()
+
+    @property
+    def address(self) -> str:
+        if self.session is None:
+            return "mixers[?]"
+        index = self.session.mixers.index(self)
+        return f"session.mixers[{index}]"
+
+    @property
+    def children(self) -> List[Component]:
+        return [*self._tracks, self._output]
+
+    @property
+    def context(self) -> Optional[AsyncServer]:
+        if self.parent is None:
+            return None
+        return self.parent._mixers[self]
diff --git a/supriya/mixers/parameters.py b/supriya/mixers/parameters.py
new file mode 100644
index 000000000..c4dce22b2
--- /dev/null
+++ b/supriya/mixers/parameters.py
@@ -0,0 +1,5 @@
+from .components import Component
+
+
+class Parameter(Component):
+    pass
diff --git a/supriya/mixers/routing.py b/supriya/mixers/routing.py
new file mode 100644
index 000000000..0aef96aa4
--- /dev/null
+++ b/supriya/mixers/routing.py
@@ -0,0 +1,254 @@
+import dataclasses
+import enum
+from typing import Generic, List, Optional, Tuple, TypeVar, Union
+
+try:
+    from typing import TypeAlias
+except ImportError:
+    from typing_extensions import TypeAlias  # noqa
+
+from ..contexts import AsyncServer, BusGroup
+from ..enums import AddAction
+from ..typing import Default
+from ..ugens import SynthDef
+from .components import A, AllocatableComponent, ComponentNames
+from .synthdefs import FB_PATCH_CABLE_2_2, PATCH_CABLE_2_2
+
+Connectable: TypeAlias = Union[AllocatableComponent, BusGroup, Default]
+
+
+class DefaultBehavior(enum.Enum):
+    PARENT = enum.auto()
+    GRANDPARENT = enum.auto()
+
+
+S = TypeVar("S", bound=Connectable)
+
+T = TypeVar("T", bound=Connectable)
+
+
+class Connection(AllocatableComponent[A], Generic[A, S, T]):
+
+    @dataclasses.dataclass
+    class State:
+        feedsback: Optional[bool] = None
+        postfader: bool = True
+        source_bus: Optional[BusGroup] = None
+        source_component: Optional[AllocatableComponent] = None
+        target_bus: Optional[BusGroup] = None
+        target_component: Optional[AllocatableComponent] = None
+
+    def __init__(
+        self,
+        *,
+        name: str,
+        source: Optional[S],
+        target: Optional[T],
+        parent: Optional[A] = None,
+        postfader: bool = True,
+    ) -> None:
+        super().__init__(parent=parent)
+        self._cached_state = self.State()
+        self._name = name
+        self._postfader = postfader
+        self._source = source
+        self._target = target
+
+    def _allocate(self, *, context: AsyncServer) -> bool:
+        if not super()._allocate(context=context):
+            return False
+        return self._reconcile(context)
+
+    def _allocate_synth(
+        self,
+        *,
+        context: AsyncServer,
+        parent: AllocatableComponent,
+        new_state: "Connection.State",
+    ) -> None:
+        self._nodes[ComponentNames.SYNTH] = parent._nodes[
+            ComponentNames.GROUP
+        ].add_synth(
+            active=parent._control_buses[ComponentNames.ACTIVE].map_symbol(),
+            add_action=AddAction.ADD_TO_TAIL,
+            in_=new_state.source_bus,
+            out=new_state.target_bus,
+            synthdef=PATCH_CABLE_2_2,
+        )
+
+    def _delete(self) -> None:
+        super()._delete()
+        for component in [
+            self._cached_state.source_component,
+            self._cached_state.target_component,
+        ]:
+            if component:
+                component._unregister_dependency(self)
+
+    def _get_synthdefs(self) -> List[SynthDef]:
+        return [FB_PATCH_CABLE_2_2, PATCH_CABLE_2_2]
+
+    def _reconcile(self, context: Optional[AsyncServer] = None) -> bool:
+        new_state = self._resolve_state(context)
+        self._reconcile_dependencies(context, new_state)
+        self._reconcile_synth(context, new_state)
+        self._cached_state = new_state
+        return self._reconcile_deferment(new_state)
+
+    def _reconcile_deferment(self, new_state: "Connection.State") -> bool:
+        if (
+            new_state.source_component
+            and new_state.target_component
+            and not (new_state.source_bus and new_state.target_bus)
+        ):
+            return False
+        return True
+
+    def _reconcile_dependencies(
+        self, context: Optional[AsyncServer], new_state: "Connection.State"
+    ) -> None:
+        for new_component, old_component in [
+            (new_state.source_component, self._cached_state.source_component),
+            (new_state.target_component, self._cached_state.target_component),
+        ]:
+            if new_component is not old_component:
+                if old_component:
+                    old_component._unregister_dependency(self)
+                if new_component:
+                    new_component._register_dependency(self)
+        if new_state.target_component and not new_state.feedsback:
+            new_state.target_component._unregister_feedback(self)
+
+    def _reconcile_synth(
+        self, context: Optional[AsyncServer], new_state: "Connection.State"
+    ) -> None:
+        if self.parent is None:
+            return
+        if context is None:
+            return
+        if new_state == self._cached_state and self._nodes.get(ComponentNames.SYNTH):
+            return
+        with context.at():
+            # Free the existing synth (if it exists)
+            if synth := self._nodes.pop(ComponentNames.SYNTH, None):
+                synth.free()
+            # Add a new synth (if source and target buses exist)
+            if new_state.source_bus and new_state.target_bus:
+                self._allocate_synth(
+                    context=context, parent=self.parent, new_state=new_state
+                )
+
+    def _resolve_default_source(
+        self, context: Optional[AsyncServer]
+    ) -> Tuple[Optional[AllocatableComponent], Optional[BusGroup]]:
+        # return self.parent
+        raise NotImplementedError
+
+    def _resolve_default_target(
+        self, context: Optional[AsyncServer]
+    ) -> Tuple[Optional[AllocatableComponent], Optional[BusGroup]]:
+        # return self.parent and self.parent.parent
+        raise NotImplementedError
+
+    def _resolve_feedback(
+        self,
+        context: Optional[AsyncServer],
+        source_component: Optional[AllocatableComponent],
+        target_component: Optional[AllocatableComponent],
+    ) -> Tuple[Optional[bool], Optional[BusGroup]]:
+        feedsback, target_bus = None, None
+        try:
+            source_order = source_component.graph_order if source_component else None
+            target_order = target_component.graph_order if target_component else None
+            feedsback = self.feedsback(source_order, target_order)
+        except Exception:
+            pass
+        if feedsback and target_component:
+            target_bus = target_component._register_feedback(context, self)
+        return feedsback, target_bus
+
+    def _resolve_source(
+        self, context: Optional[AsyncServer]
+    ) -> Tuple[Optional[AllocatableComponent], Optional[BusGroup]]:
+        # resolve source
+        source_component, source_bus = None, None
+        if isinstance(self._source, BusGroup):
+            source_bus = self._source
+        elif isinstance(self._source, AllocatableComponent):
+            source_component = self._source
+        elif isinstance(self._source, Default):
+            source_component, source_bus = self._resolve_default_source(context)
+        if source_component:
+            source_bus = source_component._audio_buses.get(ComponentNames.MAIN)
+        return source_component, source_bus
+
+    def _resolve_state(
+        self, context: Optional[AsyncServer] = None
+    ) -> "Connection.State":
+        source_component, source_bus = self._resolve_source(context)
+        target_component, target_bus = self._resolve_target(context)
+        feedsback, feedback_bus = self._resolve_feedback(
+            context, source_component, target_component
+        )
+        return self.State(
+            feedsback=feedsback,
+            postfader=self._postfader,
+            source_component=source_component,
+            source_bus=source_bus,
+            target_component=target_component,
+            target_bus=feedback_bus or target_bus,
+        )
+
+    def _resolve_target(
+        self, context: Optional[AsyncServer]
+    ) -> Tuple[Optional[AllocatableComponent], Optional[BusGroup]]:
+        target_component, target_bus = None, None
+        if isinstance(self._target, BusGroup):
+            target_bus = self._target
+        elif isinstance(self._target, AllocatableComponent):
+            target_component = self._target
+        elif isinstance(self._target, Default):
+            target_component, target_bus = self._resolve_default_target(context)
+        if target_component:
+            target_bus = target_component._audio_buses.get(ComponentNames.MAIN)
+        return target_component, target_bus
+
+    def _set_postfader(self, postfader: bool) -> None:
+        self._postfader = postfader
+        self._reconcile(self._can_allocate())
+
+    def _set_source(self, source: Optional[S]) -> None:
+        if isinstance(source, AllocatableComponent) and self.mixer is not source.mixer:
+            raise RuntimeError
+        self._source = source
+        self._reconcile(self._can_allocate())
+
+    def _set_target(self, target: Optional[T]) -> None:
+        if isinstance(target, AllocatableComponent) and self.mixer is not target.mixer:
+            raise RuntimeError
+        self._target = target
+        self._reconcile(self._can_allocate())
+
+    @classmethod
+    def feedsback(
+        cls,
+        source_order: Optional[Tuple[int, ...]],
+        target_order: Optional[Tuple[int, ...]],
+    ) -> Optional[bool]:
+        if source_order is None or target_order is None:
+            return None
+        length = min(len(target_order), len(source_order))
+        # If source_order is shallower than target_order, source_order might contain target_order
+        if len(source_order) < len(target_order):
+            return target_order[:length] <= source_order
+        # If target_order is shallower than source_order, target_order might contain source_order
+        elif len(target_order) < len(source_order):
+            return target_order < source_order[:length]
+        # If orders are same depth, check difference strictly
+        return target_order <= source_order
+
+    @property
+    def address(self) -> str:
+        if self.parent is None:
+            return self._name
+        return f"{self.parent.address}.{self._name}"
diff --git a/supriya/mixers/sessions.py b/supriya/mixers/sessions.py
new file mode 100644
index 000000000..b53df5a3f
--- /dev/null
+++ b/supriya/mixers/sessions.py
@@ -0,0 +1,199 @@
+import asyncio
+import logging
+from typing import TYPE_CHECKING, Dict, List, Optional, Set
+
+from ..clocks import AsyncClock
+from ..contexts import AsyncServer
+from ..enums import BootStatus
+from ..osc import find_free_port
+from ..ugens import SynthDef
+from .components import Component
+
+if TYPE_CHECKING:
+    from .mixers import Mixer
+
+
+logger = logging.getLogger(__name__)
+
+
+class Session(Component):
+    """
+    Top-level object.
+
+    Contains one transport.
+
+    Contains one or more contexts.
+
+    Contains one or more mixers.
+
+    Each mixer references one context.
+
+    This supports running scsynth and supernova simultaneously via two mixers.
+    """
+
+    def __init__(self) -> None:
+        from .mixers import Mixer
+
+        super().__init__()
+        self._boot_future: Optional[asyncio.Future] = None
+        self._clock = AsyncClock()
+        self._contexts: Dict[AsyncServer, List[Mixer]] = {}
+        self._lock = asyncio.Lock()
+        self._mixers: Dict[Mixer, AsyncServer] = {}
+        self._quit_future: Optional[asyncio.Future] = None
+        self._status = BootStatus.OFFLINE
+        self._synthdefs: Dict[AsyncServer, Set[SynthDef]] = {}
+        # add initial context and mixer
+        self._contexts[(context := self._add_context())] = [mixer := Mixer(parent=self)]
+        self._mixers[mixer] = context
+
+    def __repr__(self) -> str:
+        return f"<{type(self).__name__}>"
+
+    def __str__(self) -> str:
+        parts: List[str] = [f"<{type(self).__name__} status={self.status.name}>"]
+        for context, mixers in self._contexts.items():
+            parts.append(
+                f"    <{type(context).__name__} address={context.options.ip_address}:{context.options.port}>"
+            )
+            for mixer in mixers:
+                parts.extend("        " + line for line in str(mixer).splitlines())
+        return "\n".join(parts)
+
+    def _add_context(self) -> AsyncServer:
+        context = AsyncServer()
+        self._contexts[context] = []
+        self._synthdefs[context] = set()
+        return context
+
+    def _delete_mixer(self, mixer) -> None:
+        if mixer in (mixers := self._contexts.get(self._mixers.pop(mixer), [])):
+            mixers.remove(mixer)
+
+    async def add_context(self) -> AsyncServer:
+        async with self._lock:
+            context = self._add_context()
+            if self._status == BootStatus.ONLINE:
+                await context.boot(port=find_free_port())
+            return context
+
+    async def add_mixer(self, context: Optional[AsyncServer] = None) -> "Mixer":
+        from .mixers import Mixer
+
+        async with self._lock:
+            if not self._contexts:
+                context = self._add_context()
+                if self._status == BootStatus.ONLINE:
+                    await context.boot(port=find_free_port())
+            if context is None:
+                context = list(self._contexts)[0]
+            self._contexts.setdefault(context, []).append(mixer := Mixer(parent=self))
+            self._mixers[mixer] = context
+            if self._status == BootStatus.ONLINE:
+                await mixer._allocate_deep(context=context)
+            return mixer
+
+    async def boot(self) -> None:
+        async with self._lock:
+            # guard against concurrent boot / quits
+            if self._status == BootStatus.OFFLINE:
+                self._quit_future = None
+                self._boot_future = asyncio.get_running_loop().create_future()
+                self._status = BootStatus.BOOTING
+                await asyncio.gather(
+                    *[context.boot(port=find_free_port()) for context in self._contexts]
+                )
+                self._status = BootStatus.ONLINE
+                self._boot_future.set_result(True)
+                for context, mixers in self._contexts.items():
+                    for mixer in mixers:
+                        await mixer._allocate_deep(context=context)
+            elif self._boot_future is not None:  # BOOTING / ONLINE
+                await self._boot_future
+            else:  # NONREALTIME
+                raise Exception(self._status)
+
+    async def delete_context(self, context: AsyncServer) -> None:
+        async with self._lock:
+            for mixer in self._contexts.pop(context):
+                await mixer.delete()
+            await context.quit()
+
+    async def dump_components(self) -> str:
+        return ""
+
+    async def dump_tree(self) -> str:
+        # what if components and query tree stuff was intermixed?
+        # we fetch the node tree once per mixer
+        # and then the node tree needs to get partitioned by subtrees
+        if self.status != BootStatus.ONLINE:
+            raise RuntimeError
+        parts: List[str] = []
+        for context, mixers in self._contexts.items():
+            parts.append(repr(context))
+            for mixer in mixers:
+                for line in str(await mixer.dump_tree()).splitlines():
+                    parts.append(f"    {line}")
+        return "\n".join(parts)
+
+    async def quit(self) -> None:
+        async with self._lock:
+            # guard against concurrent boot / quits
+            if self._status == BootStatus.ONLINE:
+                self._boot_future = None
+                self._quit_future = asyncio.get_running_loop().create_future()
+                self._status = BootStatus.QUITTING
+                for context, mixers in self._contexts.items():
+                    for mixer in mixers:
+                        with context.at():
+                            mixer._deallocate()
+                await asyncio.gather(*[context.quit() for context in self._contexts])
+                self._status = BootStatus.OFFLINE
+                self._quit_future.set_result(True)
+            elif self._quit_future is not None:  # QUITTING / OFFLINE
+                await self._quit_future
+            elif self._status == BootStatus.OFFLINE:  # Never booted
+                return
+            else:  # NONREALTIME
+                raise Exception(self._status)
+
+    async def set_mixer_context(self, mixer: "Mixer", context: AsyncServer) -> None:
+        async with self._lock:
+            if mixer not in self._mixers:
+                raise ValueError(mixer)
+            elif context not in self._contexts:
+                raise ValueError(context)
+            if mixer in self._contexts[context]:
+                return
+            self._contexts[self._mixers[mixer]].remove(mixer)
+            async with mixer._lock:
+                mixer._deallocate_deep()
+                if self._status == BootStatus.ONLINE:
+                    await mixer._allocate_deep(context=context)
+                self._contexts[context].append(mixer)
+                self._mixers[mixer] = context
+
+    async def sync(self) -> None:
+        if self._status != BootStatus.ONLINE:
+            raise RuntimeError
+        await asyncio.gather(*[context.sync() for context in self.contexts])
+
+    @property
+    def address(self) -> str:
+        return "session"
+
+    @property
+    def children(self) -> List[Component]:
+        return list(self._mixers)
+
+    @property
+    def contexts(self) -> List[AsyncServer]:
+        return list(self._contexts)
+
+    @property
+    def mixers(self) -> List["Mixer"]:
+        return list(self._mixers)
+
+    @property
+    def status(self) -> BootStatus:
+        return self._status
diff --git a/supriya/mixers/synthdefs.py b/supriya/mixers/synthdefs.py
new file mode 100644
index 000000000..b2d446ab1
--- /dev/null
+++ b/supriya/mixers/synthdefs.py
@@ -0,0 +1,102 @@
+from ..ugens import (
+    DC,
+    Amplitude,
+    In,
+    InFeedback,
+    Linen,
+    Out,
+    Parameter,
+    ReplaceOut,
+    SynthDef,
+    SynthDefBuilder,
+)
+
+LAG_TIME = 0.005
+
+
+def build_channel_strip(channel_count: int = 2) -> SynthDef:
+    with SynthDefBuilder(
+        active=1,
+        bus=0,
+        gain=Parameter(value=0, lag=LAG_TIME),
+        gate=1,
+    ) as builder:
+        source = In.ar(
+            channel_count=channel_count,
+            bus=builder["bus"],
+        )
+        active_gate = Linen.kr(
+            attack_time=LAG_TIME,
+            gate=builder["active"],
+            release_time=LAG_TIME,
+        )
+        free_gate = Linen.kr(
+            attack_time=LAG_TIME,
+            gate=builder["gate"],
+            release_time=LAG_TIME,
+        )
+        source *= builder["gain"].db_to_amplitude()
+        source *= active_gate
+        source *= free_gate
+        ReplaceOut.ar(bus=builder["bus"], source=source)
+    return builder.build(f"supriya:channel-strip:{channel_count}")
+
+
+def build_device_dc_tester(channel_count: int = 2) -> SynthDef:
+    with SynthDefBuilder(dc=1, out=0) as builder:
+        Out.ar(bus=builder["out"], source=[DC.ar(source=builder["dc"])] * channel_count)
+    return builder.build(f"supriya:device-dc-tester:{channel_count}")
+
+
+def build_meters(channel_count: int = 2) -> SynthDef:
+    with SynthDefBuilder(in_=0, out=0) as builder:
+        Out.kr(
+            bus=builder["out"],
+            source=Amplitude.kr(
+                source=In.ar(bus=builder["in_"], channel_count=channel_count)
+            ),
+        )
+    return builder.build(f"supriya:meters:{channel_count}")
+
+
+def build_patch_cable(
+    input_channel_count: int = 2, output_channel_count: int = 2, feedback: bool = False
+) -> SynthDef:
+    # TODO: Implement up/down channel mixing
+    with SynthDefBuilder(active=1, in_=0, out=0, gain=0, gate=1) as builder:
+        if feedback:
+            source = InFeedback.ar(
+                channel_count=input_channel_count,
+                bus=builder["in_"],
+            )
+        else:
+            source = In.ar(
+                channel_count=input_channel_count,
+                bus=builder["in_"],
+            )
+        active_gate = Linen.kr(
+            attack_time=LAG_TIME,
+            gate=builder["active"],
+            release_time=LAG_TIME,
+        )
+        free_gate = Linen.kr(
+            attack_time=LAG_TIME,
+            gate=builder["gate"],
+            release_time=LAG_TIME,
+        )
+        source *= builder["gain"].db_to_amplitude()
+        source *= free_gate * active_gate
+        Out.ar(bus=builder["out"], source=source)
+
+    name = (
+        f"supriya:{'fb-' if feedback else ''}"
+        f"patch-cable:{input_channel_count}x{output_channel_count}"
+    )
+    return builder.build(name)
+
+
+CHANNEL_STRIP_2 = build_channel_strip(2)
+DEVICE_DC_TESTER_2 = build_device_dc_tester(2)
+FB_PATCH_CABLE_2_2 = build_patch_cable(2, 2, feedback=True)
+METERS_2 = build_meters(2)
+PATCH_CABLE_2_2 = build_patch_cable(2, 2)
diff --git a/supriya/mixers/tracks.py b/supriya/mixers/tracks.py
new file mode 100644
index 000000000..13140b68e
--- /dev/null
+++ b/supriya/mixers/tracks.py
@@ -0,0 +1,432 @@
+from typing import List, Optional, Tuple, Union, cast
+
+from ..contexts import AsyncServer, BusGroup
+from ..enums import AddAction
+from ..typing import DEFAULT, Default
+from ..ugens import SynthDef
+from .components import AllocatableComponent, C, Component, ComponentNames
+from .devices import DeviceContainer
+from .routing import Connection
+from .synthdefs import CHANNEL_STRIP_2, FB_PATCH_CABLE_2_2, METERS_2, PATCH_CABLE_2_2
+
+
+class TrackContainer(AllocatableComponent[C]):
+
+    def __init__(self) -> None:
+        self._tracks: List[Track] = []
+
+    def _delete_track(self, track: "Track") -> None:
+        self._tracks.remove(track)
+
+    async def add_track(self) -> "Track":
+        async with self._lock:
+            self._tracks.append(track := Track(parent=self))
+            if context := self._can_allocate():
+                await track._allocate_deep(context=context)
+            return track
+
+    @property
+    def tracks(self) -> List["Track"]:
+        return self._tracks[:]
+
+
+class TrackFeedback(Connection["Track", BusGroup, "Track"]):
+    def __init__(
+        self,
+        *,
+        parent: "Track",
+        source: Optional[BusGroup] = None,
+    ) -> None:
+        super().__init__(
+            name="feedback",
+            parent=parent,
+            source=source,
+            target=parent,
+        )
+
+    def _allocate_synth(
+        self,
+        *,
+        context: AsyncServer,
+        parent: AllocatableComponent,
+        new_state: Connection.State,
+    ) -> None:
+        self._nodes[ComponentNames.SYNTH] = parent._nodes[
+            ComponentNames.GROUP
+        ].add_synth(
+            active=parent._control_buses[ComponentNames.ACTIVE].map_symbol(),
+            add_action=AddAction.ADD_TO_HEAD,
+            in_=new_state.source_bus,
+            out=new_state.target_bus,
+            synthdef=FB_PATCH_CABLE_2_2,
+        )
+
+
+class TrackInput(Connection["Track", Union[BusGroup, TrackContainer], "Track"]):
+
+    def __init__(
+        self,
+        *,
+        parent: "Track",
+        source: Optional[Union[BusGroup, "Track"]] = None,
+    ) -> None:
+        super().__init__(
+            name="input",
+            parent=parent,
+            source=source,
+            target=parent,
+        )
+
+    def _allocate_synth(
+        self,
+        *,
+        context: AsyncServer,
+        parent: AllocatableComponent,
+        new_state: Connection.State,
+    ) -> None:
+        self._nodes[ComponentNames.SYNTH] = parent._nodes[
+            ComponentNames.TRACKS
+        ].add_synth(
+            active=parent._control_buses[ComponentNames.ACTIVE].map_symbol(),
+            add_action=AddAction.ADD_BEFORE,
+            in_=new_state.source_bus,
+            out=new_state.target_bus,
+            synthdef=PATCH_CABLE_2_2,
+        )
+
+    async def set_source(self, source: Optional[Union[BusGroup, "Track"]]) -> None:
+        async with self._lock:
+            if source is self.parent:
+                raise RuntimeError
+            self._set_source(source)
+
+
+class TrackOutput(
+    Connection["Track", "Track", Union[BusGroup, Default, TrackContainer]]
+):
+
+    def __init__(
+        self,
+        *,
+        parent: "Track",
+        target: Optional[Union[BusGroup, Default, TrackContainer]] = DEFAULT,
+    ) -> None:
+        super().__init__(
+            name="output",
+            parent=parent,
+            source=parent,
+            target=target,
+        )
+
+    def _resolve_default_target(
+        self, context: Optional[AsyncServer]
+    ) -> Tuple[Optional[AllocatableComponent], Optional[BusGroup]]:
+        return (self.parent and self.parent.parent), None
+
+    async def set_target(
+        self, target: Optional[Union[BusGroup, Default, TrackContainer]]
+    ) -> None:
+        async with self._lock:
+            if target is self.parent:
+                raise RuntimeError
+            self._set_target(target)
+
+
+class TrackSend(Connection["Track", "Track", TrackContainer]):
+    def __init__(
+        self,
+        *,
+        parent: "Track",
+        target: TrackContainer,
+        postfader: bool = True,
+    ) -> None:
+        super().__init__(
+            name="send",
+            parent=parent,
+            postfader=postfader,
+            source=parent,
+            target=target,
+        )
+
+    def _allocate_synth(
+        self,
+        *,
+        context: AsyncServer,
+        parent: AllocatableComponent,
+        new_state: Connection.State,
+    ) -> None:
+        self._nodes[ComponentNames.SYNTH] = parent._nodes[
+            ComponentNames.CHANNEL_STRIP
+        ].add_synth(
+            active=parent._control_buses[ComponentNames.ACTIVE].map_symbol(),
+            add_action=(
+                AddAction.ADD_AFTER if new_state.postfader else AddAction.ADD_BEFORE
+            ),
+            in_=new_state.source_bus,
+            out=new_state.target_bus,
+            synthdef=PATCH_CABLE_2_2,
+        )
+
+    def _resolve_default_source(
+        self, context: Optional[AsyncServer]
+    ) -> Tuple[Optional[AllocatableComponent], Optional[BusGroup]]:
+        return self.parent, None
+
+    async def delete(self) -> None:
+        async with self._lock:
+            if self._parent is not None and self in self._parent._sends:
+                self._parent._sends.remove(self)
+            self._delete()
+
+    async def set_postfader(self, postfader: bool) -> None:
+        async with self._lock:
+            self._set_postfader(postfader)
+
+    async def set_target(self, target: TrackContainer) -> None:
+        async with self._lock:
+            if target is self.parent:
+                raise RuntimeError
+            self._set_target(target)
+
+    @property
+    def address(self) -> str:
+        if self.parent is None:
+            return "sends[?]"
+        index = self.parent.sends.index(self)
+        return f"{self.parent.address}.sends[{index}]"
+
+    @property
+    def postfader(self) -> bool:
+        return self._postfader
+
+    @property
+    def target(self) -> Union[AllocatableComponent, BusGroup]:
+        # TODO: Can this be parameterized via generics?
+        return cast(Union[AllocatableComponent, BusGroup], self._target)
+
+
+class Track(TrackContainer[TrackContainer], DeviceContainer):
+
+    # TODO: add_device() -> Device
+    # TODO: add_send(destination: Track) -> Send
+    # TODO: group_devices(index: int, count: int) -> Rack
+    # TODO: group_tracks(index: int, count: int) -> Track
+    # TODO: set_channel_count(self, channel_count: Optional[ChannelCount] = None) -> None
+    # TODO: set_input(None | Default | Track | BusGroup)
+
+    def __init__(
+        self,
+        *,
+        parent: Optional[TrackContainer] = None,
+    ) -> None:
+        AllocatableComponent.__init__(self, parent=parent)
+        DeviceContainer.__init__(self)
+        TrackContainer.__init__(self)
+        self._feedback = TrackFeedback(parent=self)
+        self._input = TrackInput(parent=self)
+        self._output = TrackOutput(parent=self)
+        # TODO: Are sends the purview of track containers in general?
+        self._sends: List[TrackSend] = []
+
+    def _allocate(self, *, context: AsyncServer) -> bool:
+        if not super()._allocate(context=context):
+            return False
+        elif self.parent is None:
+            raise RuntimeError
+        main_audio_bus = self._get_audio_bus(
+            context, name=ComponentNames.MAIN, can_allocate=True
+        )
+        active_control_bus = self._get_control_bus(
+            context, name=ComponentNames.ACTIVE, can_allocate=True
+        )
+        gain_control_bus = self._get_control_bus(
+            context, name=ComponentNames.GAIN, can_allocate=True
+        )
+        input_levels_control_bus = self._get_control_bus(
+            context,
+            name=ComponentNames.INPUT_LEVELS,
+            can_allocate=True,
+            channel_count=2,
+        )
+        output_levels_control_bus = self._get_control_bus(
+            context,
+            name=ComponentNames.OUTPUT_LEVELS,
+            can_allocate=True,
+            channel_count=2,
+        )
+        target_node = self.parent._nodes[ComponentNames.TRACKS]
+        with context.at():
+            active_control_bus.set(1.0)
+            gain_control_bus.set(0.0)
+            input_levels_control_bus.set(0.0)
+            output_levels_control_bus.set(0.0)
+            self._nodes[ComponentNames.GROUP] = group = target_node.add_group(
+                add_action=AddAction.ADD_TO_TAIL
+            )
+            self._nodes[ComponentNames.TRACKS] = tracks = group.add_group(
+                add_action=AddAction.ADD_TO_HEAD
+            )
+            self._nodes[ComponentNames.DEVICES] = group.add_group(
+                add_action=AddAction.ADD_TO_TAIL
+            )
+            self._nodes[ComponentNames.CHANNEL_STRIP] = channel_strip = group.add_synth(
+                add_action=AddAction.ADD_TO_TAIL,
+                bus=main_audio_bus,
+                active=active_control_bus.map_symbol(),
+                gain=gain_control_bus.map_symbol(),
+                synthdef=CHANNEL_STRIP_2,
+            )
+            self._nodes[ComponentNames.INPUT_LEVELS] = tracks.add_synth(
+                add_action=AddAction.ADD_AFTER,
+                synthdef=METERS_2,
+                in_=self._audio_buses[ComponentNames.MAIN],
+                out=input_levels_control_bus,
+            )
+            self._nodes[ComponentNames.OUTPUT_LEVELS] = channel_strip.add_synth(
+                add_action=AddAction.ADD_AFTER,
+                synthdef=METERS_2,
+                in_=self._audio_buses[ComponentNames.MAIN],
+                out=output_levels_control_bus,
+            )
+        return True
+
+    def _get_synthdefs(self) -> List[SynthDef]:
+        return [
+            CHANNEL_STRIP_2,
+            METERS_2,
+        ]
+
+    def _register_feedback(
+        self, context: Optional[AsyncServer], dependent: "Component"
+    ) -> Optional[BusGroup]:
+        super()._register_feedback(context, dependent)
+        # check if feedback should be setup
+        if not context:
+            return None
+        if self._feedback_dependents:
+            self._feedback._set_source(
+                self._get_audio_bus(
+                    context, name=ComponentNames.FEEDBACK, can_allocate=True
+                )
+            )
+        return self._get_audio_bus(context, name=ComponentNames.FEEDBACK)
+
+    def _unregister_feedback(self, dependent: "Component") -> bool:
+        if should_tear_down := super()._unregister_feedback(dependent):
+            # check if feedback should be torn down
+            if bus_group := self._audio_buses.get(ComponentNames.FEEDBACK):
+                bus_group.free()
+            self._feedback._set_source(None)
+        return should_tear_down
+
+    async def add_send(
+        self, target: TrackContainer, postfader: bool = True
+    ) -> TrackSend:
+        async with self._lock:
+            self._sends.append(
+                send := TrackSend(parent=self, postfader=postfader, target=target)
+            )
+            if context := self._can_allocate():
+                await send._allocate_deep(context=context)
+            return send
+
+    async def delete(self) -> None:
+        # TODO: What are delete semantics actually?
+        async with self._lock:
+            if self._parent is not None:
+                self._parent._delete_track(self)
+            self._delete()
+
+    async def move(self, parent: TrackContainer, index: int) -> None:
+        async with self._lock:
+            # Validate if moving is possible
+            if self.mixer is not parent.mixer:
+                raise RuntimeError
+            elif self in parent.parentage:
+                raise RuntimeError
+            elif index < 0 or index > len(parent.tracks):
+                raise RuntimeError
+            # Reconfigure parentage and bail if this is a no-op
+            old_parent, old_index = self._parent, 0
+            if old_parent is not None:
+                old_index = old_parent._tracks.index(self)
+            if old_parent is parent and old_index == index:
+                return  # Bail
+            if old_parent is not None:
+                old_parent._tracks.remove(self)
+            self._parent = parent
+            parent._tracks.insert(index, self)
+            # Apply changes against the context
+            if (context := self._can_allocate()) is not None:
+                if index == 0:
+                    node_id = self._parent._nodes[ComponentNames.TRACKS]
+                    add_action = AddAction.ADD_TO_HEAD
+                else:
+                    node_id = self._parent._tracks[index - 1]._nodes[
+                        ComponentNames.GROUP
+                    ]
+                    add_action = AddAction.ADD_AFTER
+                with context.at():
+                    self._nodes[ComponentNames.GROUP].move(
+                        target_node=node_id, add_action=add_action
+                    )
+            for component in self._dependents:
+                component._reconcile(context)
+
+    async def set_active(self, active: bool = True) -> None:
+        async with self._lock:
+            pass
+
+    async def set_input(self, input_: Optional[Union[BusGroup, "Track"]]) -> None:
+        await self._input.set_source(input_)
+
+    async def set_output(
+        self, output: Optional[Union[Default, TrackContainer]]
+    ) -> None:
+        await self._output.set_target(output)
+
+    async def set_soloed(self, soloed: bool = True, exclusive: bool = True) -> None:
+        async with self._lock:
+            pass
+
+    async def ungroup(self) -> None:
+        async with self._lock:
+            pass
+
+    @property
+    def address(self) -> str:
+        if self.parent is None:
+            return "tracks[?]"
+        index = self.parent.tracks.index(self)
+        return f"{self.parent.address}.tracks[{index}]"
+
+    @property
+    def children(self) -> List[Component]:
+        prefader_sends = []
+        postfader_sends = []
+        for send in self._sends:
+            if send.postfader:
+                postfader_sends.append(send)
+            else:
+                prefader_sends.append(send)
+        return [
+            self._feedback,
+            self._input,
+            *self._tracks,
+            *self._devices,
+            *prefader_sends,
+            self._output,
+            *postfader_sends,
+        ]
+
+    @property
+    def input_(self) -> Optional[Union[BusGroup, TrackContainer]]:
+        return self._input._source
+
+    @property
+    def output(self) -> Optional[Union[BusGroup, Default, TrackContainer]]:
+        return self._output._target
+
+    @property
+    def sends(self) -> List[TrackSend]:
+        return self._sends[:]
diff --git a/supriya/typing.py b/supriya/typing.py
index c36c22045..2edec2d02 100644
--- a/supriya/typing.py
+++ b/supriya/typing.py
@@ -41,10 +41,16 @@ class Default:
     pass
 
 
+DEFAULT = Default()
+
+
 class Missing:
     pass
 
 
+MISSING = Missing()
+
+
 @runtime_checkable
 class SupportsOsc(Protocol):
     def to_osc(self) -> Union["OscBundle", "OscMessage"]:
diff --git a/tests/mixers/__init__.py b/tests/mixers/__init__.py
new file mode 100644
index 000000000..e69de29bb
diff --git a/tests/mixers/conftest.py b/tests/mixers/conftest.py
new file mode 100644
index 000000000..a60c35dcf
--- /dev/null
+++ b/tests/mixers/conftest.py
@@ -0,0 +1,66 @@
+import contextlib
+import difflib
+from typing import List, Optional, Union
+
+import pytest
+from uqbar.strings import normalize
+
+from supriya import AsyncServer, OscBundle, OscMessage
+from supriya.mixers import Session
+from supriya.mixers.mixers import Mixer
+from supriya.mixers.tracks import Track
+
+
+@contextlib.contextmanager
+def capture(context: Optional[AsyncServer]):
+    entries: List[Union[OscBundle, OscMessage]] = []
+    if context is None:
+        yield entries
+    else:
+        with context.osc_protocol.capture() as transcript:
+            yield entries
+    entries.extend(transcript.filtered(received=False, status=False))
+
+
+async def debug_tree(session: Session, label: str = "initial tree") -> str:
+    tree = str(await session.dump_tree())
+    for i, context in enumerate(session.contexts):
+        tree = tree.replace(repr(context), f"<session.contexts[{i}]>")
+    print(f"{label}:\n{tree}")
+    return tree
+
+
+async def assert_diff(
+    session: Session, expected_diff: str, expected_initial_tree: str
+) -> None:
+    await session.sync()
+    print(f"expected initial tree:\n{normalize(expected_initial_tree)}")
+    actual_tree = await debug_tree(session, "actual tree")
+    actual_diff = "".join(
+        difflib.unified_diff(
+            normalize(expected_initial_tree).splitlines(True),
+            actual_tree.splitlines(True),
+            tofile="mutation",
+            fromfile="initial",
+        )
+    )
+    print(f"actual diff:\n{normalize(actual_diff)}")
+    assert normalize(expected_diff) == normalize(actual_diff)
+
+
+does_not_raise = contextlib.nullcontext()
+
+
+@pytest.fixture
+def mixer(session: Session) -> Mixer:
+    return session.mixers[0]
+
+
+@pytest.fixture
+def session() -> Session:
+    return Session()
+
+
+@pytest.fixture
+def track(mixer: Mixer) -> Track:
+    return mixer.tracks[0]
diff --git a/tests/mixers/test_Connection.py b/tests/mixers/test_Connection.py
new file mode 100644
index 000000000..070878fda
--- /dev/null
+++ b/tests/mixers/test_Connection.py
@@ -0,0 +1,56 @@
+from typing import Dict
+
+import pytest
+
+from supriya.mixers.components import Component
+from supriya.mixers.mixers import Mixer
+from supriya.mixers.routing import Connection
+
+
+@pytest.mark.parametrize(
+    "source_name, target_name, feedsback",
+    [
+        ("mixer", "mixer", True),
+        ("mixer", "track_one", True),
+        ("mixer", "track_two", True),
+        ("mixer", "track_one_child", True),
+        ("mixer", "track_two_child", True),
+        ("track_one", "mixer", False),
+        ("track_one", "track_one", True),
+        ("track_one", "track_two", False),
+        ("track_one", "track_one_child", True),
+        ("track_one", "track_two_child", False),
+        ("track_two", "mixer", False),
+        ("track_two", "track_one", True),
+        ("track_two", "track_two", True),
+        ("track_two", "track_one_child", True),
+        ("track_two", "track_two_child", True),
+        ("track_one_child", "mixer", False),
+        ("track_one_child", "track_one", False),
+        ("track_one_child", "track_two", False),
+        ("track_one_child", "track_one_child", True),
+        ("track_one_child", "track_two_child", False),
+        ("track_two_child", "mixer", False),
+        ("track_two_child", "track_one", True),
+        ("track_two_child", "track_two", False),
+        ("track_two_child", "track_one_child", True),
+        ("track_two_child", "track_two_child", True),
+    ],
+)
+@pytest.mark.asyncio
+async def test_Connection_feedsback(
+    source_name: str, target_name: str, feedsback: bool, mixer: Mixer
+) -> None:
+    components: Dict[str, Component] = {
+        "mixer": mixer,
+        "track_one": (track_one := mixer.tracks[0]),
+        "track_two": (track_two := await mixer.add_track()),
+        "track_one_child": await track_one.add_track(),
+        "track_two_child": await track_two.add_track(),
+    }
+    source = components[source_name]
+    target = components[target_name]
+    assert Connection.feedsback(source.graph_order, target.graph_order) == feedsback, (
+        source_name,
+        target_name,
+    )
diff --git a/tests/mixers/test_Mixer.py b/tests/mixers/test_Mixer.py
new file mode 100644
index 000000000..44c13299e
--- /dev/null
+++ b/tests/mixers/test_Mixer.py
@@ -0,0 +1,199 @@
+from typing import List, Union
+
+import pytest
+
+from supriya import OscBundle, OscMessage
+from supriya.mixers import Session
+from supriya.mixers.mixers import Mixer
+
+from .conftest import assert_diff, capture, debug_tree
+
+
+@pytest.mark.parametrize("online", [False, True])
+@pytest.mark.parametrize(
+    "expected_commands, expected_diff",
+    [
+        (
+            [
+                OscBundle(
+                    contents=(
+                        OscMessage("/c_set", 11, 1.0, 12, 0.0),
+                        OscMessage("/c_fill", 13, 2, 0.0, 15, 2, 0.0),
+                        OscMessage(
+                            "/g_new", 1014, 1, 1001, 1015, 0, 1014, 1016, 1, 1014
+                        ),
+                        OscMessage(
+                            "/s_new",
+                            "supriya:channel-strip:2",
+                            1017,
+                            1,
+                            1014,
+                            "active",
+                            "c11",
+                            "bus",
+                            20.0,
+                            "gain",
+                            "c12",
+                        ),
+                        OscMessage(
+                            "/s_new",
+                            "supriya:meters:2",
+                            1018,
+                            3,
+                            1015,
+                            "in_",
+                            20.0,
+                            "out",
+                            13.0,
+                        ),
+                        OscMessage(
+                            "/s_new",
+                            "supriya:meters:2",
+                            1019,
+                            3,
+                            1017,
+                            "in_",
+                            20.0,
+                            "out",
+                            15.0,
+                        ),
+                    ),
+                ),
+                OscMessage(
+                    "/s_new",
+                    "supriya:patch-cable:2x2",
+                    1020,
+                    1,
+                    1014,
+                    "active",
+                    "c11",
+                    "in_",
+                    20.0,
+                    "out",
+                    16.0,
+                ),
+            ],
+            """
+            --- initial
+            +++ mutation
+            @@ -12,6 +12,17 @@
+                                 in_: 18.0, out: 9.0
+                             1012 supriya:patch-cable:2x2 (session.mixers[0].tracks[0].output:synth)
+                                 active: c5, gain: 0.0, gate: 1.0, in_: 18.0, out: 16.0
+            +            1014 group (session.mixers[0].tracks[1]:group)
+            +                1015 group (session.mixers[0].tracks[1]:tracks)
+            +                1018 supriya:meters:2 (session.mixers[0].tracks[1]:input-levels)
+            +                    in_: 20.0, out: 13.0
+            +                1016 group (session.mixers[0].tracks[1]:devices)
+            +                1017 supriya:channel-strip:2 (session.mixers[0].tracks[1]:channel-strip)
+            +                    active: c11, bus: 20.0, gain: c12, gate: 1.0
+            +                1019 supriya:meters:2 (session.mixers[0].tracks[1]:output-levels)
+            +                    in_: 20.0, out: 15.0
+            +                1020 supriya:patch-cable:2x2 (session.mixers[0].tracks[1].output:synth)
+            +                    active: c11, gain: 0.0, gate: 1.0, in_: 20.0, out: 16.0
+                     1004 supriya:meters:2 (session.mixers[0]:input-levels)
+                         in_: 16.0, out: 1.0
+                     1002 group (session.mixers[0]:devices)
+            """,
+        ),
+    ],
+)
+@pytest.mark.asyncio
+async def test_Mixer_add_track(
+    expected_commands: List[Union[OscBundle, OscMessage]],
+    expected_diff: str,
+    mixer: Mixer,
+    online: bool,
+    session: Session,
+) -> None:
+    # Pre-conditions
+    print("Pre-conditions")
+    if online:
+        await session.boot()
+        await debug_tree(session)
+    # Operation
+    print("Operation")
+    with capture(mixer.context) as commands:
+        track = await mixer.add_track()
+    # Post-conditions
+    print("Post-conditions")
+    assert track in mixer.tracks
+    assert track.parent is mixer
+    assert mixer.tracks[-1] is track
+    if not online:
+        return
+    await assert_diff(
+        session,
+        expected_diff,
+        expected_initial_tree="""
+        <session.contexts[0]>
+            NODE TREE 1000 group (session.mixers[0]:group)
+                1001 group (session.mixers[0]:tracks)
+                    1006 group (session.mixers[0].tracks[0]:group)
+                        1007 group (session.mixers[0].tracks[0]:tracks)
+                        1010 supriya:meters:2 (session.mixers[0].tracks[0]:input-levels)
+                            in_: 18.0, out: 7.0
+                        1008 group (session.mixers[0].tracks[0]:devices)
+                        1009 supriya:channel-strip:2 (session.mixers[0].tracks[0]:channel-strip)
+                            active: c5, bus: 18.0, gain: c6, gate: 1.0
+                        1011 supriya:meters:2 (session.mixers[0].tracks[0]:output-levels)
+                            in_: 18.0, out: 9.0
+                        1012 supriya:patch-cable:2x2 (session.mixers[0].tracks[0].output:synth)
+                            active: c5, gain: 0.0, gate: 1.0, in_: 18.0, out: 16.0
+                1004 supriya:meters:2 (session.mixers[0]:input-levels)
+                    in_: 16.0, out: 1.0
+                1002 group (session.mixers[0]:devices)
+                1003 supriya:channel-strip:2 (session.mixers[0]:channel-strip)
+                    active: 1.0, bus: 16.0, gain: c0, gate: 1.0
+                1005 supriya:meters:2 (session.mixers[0]:output-levels)
+                    in_: 16.0, out: 3.0
+                1013 supriya:patch-cable:2x2 (session.mixers[0].output:synth)
+                    active: 1.0, gain: 0.0, gate: 1.0, in_: 16.0, out: 0.0
+        """,
+    )
+    assert commands == expected_commands
+
+
+@pytest.mark.xfail
+@pytest.mark.parametrize("online", [False, True])
+@pytest.mark.parametrize(
+    "expected_commands, expected_diff",
+    [
+        (
+            [
+                OscMessage("/n_set", 1000, "gate", 0.0),
+                OscMessage("/n_set", 1004, "gate", 0.0),
+            ],
+            "",
+        ),
+    ],
+)
+@pytest.mark.asyncio
+async def test_Mixer_delete(
+    expected_commands: List[Union[OscBundle, OscMessage]],
+    expected_diff: str,
+    mixer: Mixer,
+    online: bool,
+    session: Session,
+) -> None:
+    # Pre-conditions
+    print("Pre-conditions")
+    if online:
+        await session.boot()
+    # Operation
+    print("Operation")
+    with capture(mixer.context) as commands:
+        await mixer.delete()
+    # Post-conditions
+    print("Post-conditions")
+    if not online:
+        raise Exception
+    await assert_diff(
+        session,
+        expected_diff,
+        expected_initial_tree="""
+        <session.contexts[0]>
+        """,
+    )
+    assert commands == expected_commands
+    raise Exception
diff --git a/tests/mixers/test_Session.py b/tests/mixers/test_Session.py
new file mode 100644
index 000000000..91639f10e
--- /dev/null
+++ b/tests/mixers/test_Session.py
@@ -0,0 +1,475 @@
+from contextlib import nullcontext as does_not_raise
+
+import pytest
+from uqbar.strings import normalize
+
+from supriya.enums import BootStatus
+from supriya.mixers import Session
+
+from .conftest import assert_diff, debug_tree
+
+
+@pytest.mark.parametrize("online", [False, True])
+@pytest.mark.asyncio
+async def test_Session_boot(online: bool, session: Session) -> None:
+    # Pre-conditions
+    assert session.status == BootStatus.OFFLINE
+    if online:
+        await session.boot()
+        assert session.status == BootStatus.ONLINE
+    # Operation
+    await session.boot()  # idempotent
+    # Post-conditions
+    assert session.status == BootStatus.ONLINE
+    assert await session.dump_tree() == normalize(
+        f"""
+        {session.contexts[0]!r}
+            NODE TREE 1000 group (session.mixers[0]:group)
+                1001 group (session.mixers[0]:tracks)
+                    1006 group (session.mixers[0].tracks[0]:group)
+                        1007 group (session.mixers[0].tracks[0]:tracks)
+                        1010 supriya:meters:2 (session.mixers[0].tracks[0]:input-levels)
+                            in_: 18.0, out: 7.0
+                        1008 group (session.mixers[0].tracks[0]:devices)
+                        1009 supriya:channel-strip:2 (session.mixers[0].tracks[0]:channel-strip)
+                            active: c5, bus: 18.0, gain: c6, gate: 1.0
+                        1011 supriya:meters:2 (session.mixers[0].tracks[0]:output-levels)
+                            in_: 18.0, out: 9.0
+                        1012 supriya:patch-cable:2x2 (session.mixers[0].tracks[0].output:synth)
+                            active: c5, gain: 0.0, gate: 1.0, in_: 18.0, out: 16.0
+                1004 supriya:meters:2 (session.mixers[0]:input-levels)
+                    in_: 16.0, out: 1.0
+                1002 group (session.mixers[0]:devices)
+                1003 supriya:channel-strip:2 (session.mixers[0]:channel-strip)
+                    active: 1.0, bus: 16.0, gain: c0, gate: 1.0
+                1005 supriya:meters:2 (session.mixers[0]:output-levels)
+                    in_: 16.0, out: 3.0
+                1013 supriya:patch-cable:2x2 (session.mixers[0].output:synth)
+                    active: 1.0, gain: 0.0, gate: 1.0, in_: 16.0, out: 0.0
+        """
+    )
+
+
+@pytest.mark.parametrize("online", [False, True])
+@pytest.mark.asyncio
+async def test_Session_quit(online: bool, session: Session) -> None:
+    # Pre-conditions
+    assert session.status == BootStatus.OFFLINE
+    if online:
+        await session.boot()
+        assert session.status == BootStatus.ONLINE
+    # Operation
+    await session.quit()
+    # Post-conditions
+    assert session.status == BootStatus.OFFLINE
+    with pytest.raises(RuntimeError):
+        assert await session.dump_tree()
+
+
+@pytest.mark.parametrize(
+    "online, expectation",
+    [
+        (False, pytest.raises(RuntimeError)),
+        (True, does_not_raise()),
+    ],
+)
+@pytest.mark.asyncio
+async def test_Session_add_context(expectation, online: bool, session: Session) -> None:
+    # Pre-conditions
+    if online:
+        await session.boot()
+    assert len(session.contexts) == 1
+    # Operation
+    context = await session.add_context()
+    # Post-conditions
+    assert len(session.contexts) == 2
+    assert context in session.contexts
+    assert context.boot_status == session.status
+    with expectation:
+        assert await session.dump_tree() == normalize(
+            f"""
+            {session.contexts[0]!r}
+                NODE TREE 1000 group (session.mixers[0]:group)
+                    1001 group (session.mixers[0]:tracks)
+                        1006 group (session.mixers[0].tracks[0]:group)
+                            1007 group (session.mixers[0].tracks[0]:tracks)
+                            1010 supriya:meters:2 (session.mixers[0].tracks[0]:input-levels)
+                                in_: 18.0, out: 7.0
+                            1008 group (session.mixers[0].tracks[0]:devices)
+                            1009 supriya:channel-strip:2 (session.mixers[0].tracks[0]:channel-strip)
+                                active: c5, bus: 18.0, gain: c6, gate: 1.0
+                            1011 supriya:meters:2 (session.mixers[0].tracks[0]:output-levels)
+                                in_: 18.0, out: 9.0
+                            1012 supriya:patch-cable:2x2 (session.mixers[0].tracks[0].output:synth)
+                                active: c5, gain: 0.0, gate: 1.0, in_: 18.0, out: 16.0
+                    1004 supriya:meters:2 (session.mixers[0]:input-levels)
+                        in_: 16.0, out: 1.0
+                    1002 group (session.mixers[0]:devices)
+                    1003 supriya:channel-strip:2 (session.mixers[0]:channel-strip)
+                        active: 1.0, bus: 16.0, gain: c0, gate: 1.0
+                    1005 supriya:meters:2 (session.mixers[0]:output-levels)
+                        in_: 16.0, out: 3.0
+                    1013 supriya:patch-cable:2x2 (session.mixers[0].output:synth)
+                        active: 1.0, gain: 0.0, gate: 1.0, in_: 16.0, out: 0.0
+            {session.contexts[1]!r}
+            """
+        )
+
+
+@pytest.mark.parametrize(
+    "online, expectation, reuse_context",
+    [
+        (False, pytest.raises(RuntimeError), False),
+        (True, does_not_raise(), False),
+        (True, does_not_raise(), True),
+    ],
+)
+@pytest.mark.asyncio
+async def test_Session_add_mixer(
+    expectation, online: bool, reuse_context, session: Session
+) -> None:
+    # Pre-conditions
+    if online:
+        await session.boot()
+    await session.add_context()
+    assert len(session.mixers) == 1
+    # Operation
+    await session.add_mixer(context=None if reuse_context else session.contexts[1])
+    # Post-conditions
+    assert len(session.mixers) == 2
+    with expectation:
+        if not reuse_context:
+            assert await session.dump_tree() == normalize(
+                f"""
+                {session.contexts[0]!r}
+                    NODE TREE 1000 group (session.mixers[0]:group)
+                        1001 group (session.mixers[0]:tracks)
+                            1006 group (session.mixers[0].tracks[0]:group)
+                                1007 group (session.mixers[0].tracks[0]:tracks)
+                                1010 supriya:meters:2 (session.mixers[0].tracks[0]:input-levels)
+                                    in_: 18.0, out: 7.0
+                                1008 group (session.mixers[0].tracks[0]:devices)
+                                1009 supriya:channel-strip:2 (session.mixers[0].tracks[0]:channel-strip)
+                                    active: c5, bus: 18.0, gain: c6, gate: 1.0
+                                1011 supriya:meters:2 (session.mixers[0].tracks[0]:output-levels)
+                                    in_: 18.0, out: 9.0
+                                1012 supriya:patch-cable:2x2 (session.mixers[0].tracks[0].output:synth)
+                                    active: c5, gain: 0.0, gate: 1.0, in_: 18.0, out: 16.0
+                        1004 supriya:meters:2 (session.mixers[0]:input-levels)
+                            in_: 16.0, out: 1.0
+                        1002 group (session.mixers[0]:devices)
+                        1003 supriya:channel-strip:2 (session.mixers[0]:channel-strip)
+                            active: 1.0, bus: 16.0, gain: c0, gate: 1.0
+                        1005 supriya:meters:2 (session.mixers[0]:output-levels)
+                            in_: 16.0, out: 3.0
+                        1013 supriya:patch-cable:2x2 (session.mixers[0].output:synth)
+                            active: 1.0, gain: 0.0, gate: 1.0, in_: 16.0, out: 0.0
+                {session.contexts[1]!r}
+                    NODE TREE 1000 group (session.mixers[1]:group)
+                        1001 group (session.mixers[1]:tracks)
+                            1006 group (session.mixers[1].tracks[0]:group)
+                                1007 group (session.mixers[1].tracks[0]:tracks)
+                                1010 supriya:meters:2 (session.mixers[1].tracks[0]:input-levels)
+                                    in_: 18.0, out: 7.0
+                                1008 group (session.mixers[1].tracks[0]:devices)
+                                1009 supriya:channel-strip:2 (session.mixers[1].tracks[0]:channel-strip)
+                                    active: c5, bus: 18.0, gain: c6, gate: 1.0
+                                1011 supriya:meters:2 (session.mixers[1].tracks[0]:output-levels)
+                                    in_: 18.0, out: 9.0
+                                1012 supriya:patch-cable:2x2 (session.mixers[1].tracks[0].output:synth)
+                                    active: c5, gain: 0.0, gate: 1.0, in_: 18.0, out: 16.0
+                        1004 supriya:meters:2 (session.mixers[1]:input-levels)
+                            in_: 16.0, out: 1.0
+                        1002 group (session.mixers[1]:devices)
+                        1003 supriya:channel-strip:2 (session.mixers[1]:channel-strip)
+                            active: 1.0, bus: 16.0, gain: c0, gate: 1.0
+                        1005 supriya:meters:2 (session.mixers[1]:output-levels)
+                            in_: 16.0, out: 3.0
+                        1013 supriya:patch-cable:2x2 (session.mixers[1].output:synth)
+                            active: 1.0, gain: 0.0, gate: 1.0, in_: 16.0, out: 0.0
+                """
+            )
+        else:
+            assert await session.dump_tree() == normalize(
+                f"""
+                {session.contexts[0]!r}
+                    NODE TREE 1000 group (session.mixers[0]:group)
+                        1001 group (session.mixers[0]:tracks)
+                            1006 group (session.mixers[0].tracks[0]:group)
+                                1007 group (session.mixers[0].tracks[0]:tracks)
+                                1010 supriya:meters:2 (session.mixers[0].tracks[0]:input-levels)
+                                    in_: 18.0, out: 7.0
+                                1008 group (session.mixers[0].tracks[0]:devices)
+                                1009 supriya:channel-strip:2 (session.mixers[0].tracks[0]:channel-strip)
+                                    active: c5, bus: 18.0, gain: c6, gate: 1.0
+                                1011 supriya:meters:2 (session.mixers[0].tracks[0]:output-levels)
+                                    in_: 18.0, out: 9.0
+                                1012 supriya:patch-cable:2x2 (session.mixers[0].tracks[0].output:synth)
+                                    active: c5, gain: 0.0, gate: 1.0, in_: 18.0, out: 16.0
+                        1004 supriya:meters:2 (session.mixers[0]:input-levels)
+                            in_: 16.0, out: 1.0
+                        1002 group (session.mixers[0]:devices)
+                        1003 supriya:channel-strip:2 (session.mixers[0]:channel-strip)
+                            active: 1.0, bus: 16.0, gain: c0, gate: 1.0
+                        1005 supriya:meters:2 (session.mixers[0]:output-levels)
+                            in_: 16.0, out: 3.0
+                        1013 supriya:patch-cable:2x2 (session.mixers[0].output:synth)
+                            active: 1.0, gain: 0.0, gate: 1.0, in_: 16.0, out: 0.0
+                    NODE TREE 1014 group (session.mixers[1]:group)
+                        1015 group (session.mixers[1]:tracks)
+                            1020 group (session.mixers[1].tracks[0]:group)
+                                1021 group (session.mixers[1].tracks[0]:tracks)
+                                1024 supriya:meters:2 (session.mixers[1].tracks[0]:input-levels)
+                                    in_: 22.0, out: 18.0
+                                1022 group (session.mixers[1].tracks[0]:devices)
+                                1023 supriya:channel-strip:2 (session.mixers[1].tracks[0]:channel-strip)
+                                    active: c16, bus: 22.0, gain: c17, gate: 1.0
+                                1025 supriya:meters:2 (session.mixers[1].tracks[0]:output-levels)
+                                    in_: 22.0, out: 20.0
+                                1026 supriya:patch-cable:2x2 (session.mixers[1].tracks[0].output:synth)
+                                    active: c16, gain: 0.0, gate: 1.0, in_: 22.0, out: 20.0
+                        1018 supriya:meters:2 (session.mixers[1]:input-levels)
+                            in_: 20.0, out: 12.0
+                        1016 group (session.mixers[1]:devices)
+                        1017 supriya:channel-strip:2 (session.mixers[1]:channel-strip)
+                            active: 1.0, bus: 20.0, gain: c11, gate: 1.0
+                        1019 supriya:meters:2 (session.mixers[1]:output-levels)
+                            in_: 20.0, out: 14.0
+                        1027 supriya:patch-cable:2x2 (session.mixers[1].output:synth)
+                            active: 1.0, gain: 0.0, gate: 1.0, in_: 20.0, out: 0.0
+                {session.contexts[1]!r}
+                """
+            )
+
+
+@pytest.mark.parametrize(
+    "online, expectation",
+    [
+        (False, pytest.raises(RuntimeError)),
+        (True, does_not_raise()),
+    ],
+)
+@pytest.mark.asyncio
+async def test_Session_delete_context(
+    expectation, online: bool, session: Session
+) -> None:
+    # Pre-conditions
+    if online:
+        await session.boot()
+    await session.add_context()
+    # Operation
+    await session.delete_context(session.contexts[0])
+    # Post-conditions
+    assert len(session.contexts) == 1
+    assert len(session.mixers) == 0
+    with expectation:
+        assert await session.dump_tree() == normalize(
+            f"""
+            {session.contexts[0]!r}
+            """
+        )
+
+
+@pytest.mark.parametrize("online", [False, True])
+@pytest.mark.parametrize(
+    "mixer_index, context_index, expected_diff",
+    [
+        (0, 0, ""),
+        (
+            0,
+            1,
+            """
+            --- initial
+            +++ mutation
+            @@ -1,26 +1,4 @@
+             <session.contexts[0]>
+            -    NODE TREE 1000 group (session.mixers[0]:group)
+            -        1001 group (session.mixers[0]:tracks)
+            -            1006 group (session.mixers[0].tracks[0]:group)
+            -                1007 group (session.mixers[0].tracks[0]:tracks)
+            -                1010 supriya:meters:2 (session.mixers[0].tracks[0]:input-levels)
+            -                    in_: 18.0, out: 7.0
+            -                1008 group (session.mixers[0].tracks[0]:devices)
+            -                1009 supriya:channel-strip:2 (session.mixers[0].tracks[0]:channel-strip)
+            -                    active: c5, bus: 18.0, gain: c6, gate: 1.0
+            -                1011 supriya:meters:2 (session.mixers[0].tracks[0]:output-levels)
+            -                    in_: 18.0, out: 9.0
+            -                1012 supriya:patch-cable:2x2 (session.mixers[0].tracks[0].output:synth)
+            -                    active: c5, gain: 0.0, gate: 1.0, in_: 18.0, out: 16.0
+            -        1004 supriya:meters:2 (session.mixers[0]:input-levels)
+            -            in_: 16.0, out: 1.0
+            -        1002 group (session.mixers[0]:devices)
+            -        1003 supriya:channel-strip:2 (session.mixers[0]:channel-strip)
+            -            active: 1.0, bus: 16.0, gain: c0, gate: 1.0
+            -        1005 supriya:meters:2 (session.mixers[0]:output-levels)
+            -            in_: 16.0, out: 3.0
+            -        1013 supriya:patch-cable:2x2 (session.mixers[0].output:synth)
+            -            active: 1.0, gain: 0.0, gate: 1.0, in_: 16.0, out: 0.0
+                 NODE TREE 1014 group (session.mixers[1]:group)
+                     1015 group (session.mixers[1]:tracks)
+                         1020 group (session.mixers[1].tracks[0]:group)
+            @@ -43,4 +21,26 @@
+                         in_: 20.0, out: 14.0
+                     1027 supriya:patch-cable:2x2 (session.mixers[1].output:synth)
+                         active: 1.0, gain: 0.0, gate: 1.0, in_: 20.0, out: 0.0
+            -<session.contexts[1]>+<session.contexts[1]>
+            +    NODE TREE 1000 group (session.mixers[0]:group)
+            +        1001 group (session.mixers[0]:tracks)
+            +            1006 group (session.mixers[0].tracks[0]:group)
+            +                1007 group (session.mixers[0].tracks[0]:tracks)
+            +                1010 supriya:meters:2 (session.mixers[0].tracks[0]:input-levels)
+            +                    in_: 18.0, out: 7.0
+            +                1008 group (session.mixers[0].tracks[0]:devices)
+            +                1009 supriya:channel-strip:2 (session.mixers[0].tracks[0]:channel-strip)
+            +                    active: c5, bus: 18.0, gain: c6, gate: 1.0
+            +                1011 supriya:meters:2 (session.mixers[0].tracks[0]:output-levels)
+            +                    in_: 18.0, out: 9.0
+            +                1012 supriya:patch-cable:2x2 (session.mixers[0].tracks[0].output:synth)
+            +                    active: c5, gain: 0.0, gate: 1.0, in_: 18.0, out: 16.0
+            +        1004 supriya:meters:2 (session.mixers[0]:input-levels)
+            +            in_: 16.0, out: 1.0
+            +        1002 group (session.mixers[0]:devices)
+            +        1003 supriya:channel-strip:2 (session.mixers[0]:channel-strip)
+            +            active: 1.0, bus: 16.0, gain: c0, gate: 1.0
+            +        1005 supriya:meters:2 (session.mixers[0]:output-levels)
+            +            in_: 16.0, out: 3.0
+            +        1013 supriya:patch-cable:2x2 (session.mixers[0].output:synth)
+            +            active: 1.0, gain: 0.0, gate: 1.0, in_: 16.0, out: 0.0
+            """,
+        ),
+        (1, 0, ""),
+        (
+            1,
+            1,
+            """
+            --- initial
+            +++ mutation
+            @@ -21,26 +21,26 @@
+                         in_: 16.0, out: 3.0
+                     1013 supriya:patch-cable:2x2 (session.mixers[0].output:synth)
+                         active: 1.0, gain: 0.0, gate: 1.0, in_: 16.0, out: 0.0
+            -    NODE TREE 1014 group (session.mixers[1]:group)
+            -        1015 group (session.mixers[1]:tracks)
+            -            1020 group (session.mixers[1].tracks[0]:group)
+            -                1021 group (session.mixers[1].tracks[0]:tracks)
+            -                1024 supriya:meters:2 (session.mixers[1].tracks[0]:input-levels)
+            -                    in_: 22.0, out: 18.0
+            -                1022 group (session.mixers[1].tracks[0]:devices)
+            -                1023 supriya:channel-strip:2 (session.mixers[1].tracks[0]:channel-strip)
+            -                    active: c16, bus: 22.0, gain: c17, gate: 1.0
+            -                1025 supriya:meters:2 (session.mixers[1].tracks[0]:output-levels)
+            -                    in_: 22.0, out: 20.0
+            -                1026 supriya:patch-cable:2x2 (session.mixers[1].tracks[0].output:synth)
+            -                    active: c16, gain: 0.0, gate: 1.0, in_: 22.0, out: 20.0
+            -        1018 supriya:meters:2 (session.mixers[1]:input-levels)
+            -            in_: 20.0, out: 12.0
+            -        1016 group (session.mixers[1]:devices)
+            -        1017 supriya:channel-strip:2 (session.mixers[1]:channel-strip)
+            -            active: 1.0, bus: 20.0, gain: c11, gate: 1.0
+            -        1019 supriya:meters:2 (session.mixers[1]:output-levels)
+            -            in_: 20.0, out: 14.0
+            -        1027 supriya:patch-cable:2x2 (session.mixers[1].output:synth)
+            -            active: 1.0, gain: 0.0, gate: 1.0, in_: 20.0, out: 0.0
+            -<session.contexts[1]>+<session.contexts[1]>
+            +    NODE TREE 1000 group (session.mixers[1]:group)
+            +        1001 group (session.mixers[1]:tracks)
+            +            1006 group (session.mixers[1].tracks[0]:group)
+            +                1007 group (session.mixers[1].tracks[0]:tracks)
+            +                1010 supriya:meters:2 (session.mixers[1].tracks[0]:input-levels)
+            +                    in_: 18.0, out: 7.0
+            +                1008 group (session.mixers[1].tracks[0]:devices)
+            +                1009 supriya:channel-strip:2 (session.mixers[1].tracks[0]:channel-strip)
+            +                    active: c5, bus: 18.0, gain: c6, gate: 1.0
+            +                1011 supriya:meters:2 (session.mixers[1].tracks[0]:output-levels)
+            +                    in_: 18.0, out: 9.0
+            +                1012 supriya:patch-cable:2x2 (session.mixers[1].tracks[0].output:synth)
+            +                    active: c5, gain: 0.0, gate: 1.0, in_: 18.0, out: 16.0
+            +        1004 supriya:meters:2 (session.mixers[1]:input-levels)
+            +            in_: 16.0, out: 1.0
+            +        1002 group (session.mixers[1]:devices)
+            +        1003 supriya:channel-strip:2 (session.mixers[1]:channel-strip)
+            +            active: 1.0, bus: 16.0, gain: c0, gate: 1.0
+            +        1005 supriya:meters:2 (session.mixers[1]:output-levels)
+            +            in_: 16.0, out: 3.0
+            +        1013 supriya:patch-cable:2x2 (session.mixers[1].output:synth)
+            +            active: 1.0, gain: 0.0, gate: 1.0, in_: 16.0, out: 0.0
+            """,
+        ),
+    ],
+)
+@pytest.mark.asyncio
+async def test_Session_set_mixer_context(
+    context_index: int,
+    expected_diff: str,
+    mixer_index: int,
+    online: bool,
+    session: Session,
+) -> None:
+    # Pre-conditions
+    if online:
+        await session.boot()
+    await session.add_mixer()
+    await session.add_context()
+    assert len(session.contexts) == 2
+    assert len(session.mixers) == 2
+    if online:
+        await debug_tree(session)
+    # Operation
+    await session.set_mixer_context(
+        mixer=session.mixers[mixer_index], context=session.contexts[context_index]
+    )
+    # Post-conditions
+    if not online:
+        return
+    await assert_diff(
+        session,
+        expected_diff,
+        expected_initial_tree="""
+        <session.contexts[0]>
+            NODE TREE 1000 group (session.mixers[0]:group)
+                1001 group (session.mixers[0]:tracks)
+                    1006 group (session.mixers[0].tracks[0]:group)
+                        1007 group (session.mixers[0].tracks[0]:tracks)
+                        1010 supriya:meters:2 (session.mixers[0].tracks[0]:input-levels)
+                            in_: 18.0, out: 7.0
+                        1008 group (session.mixers[0].tracks[0]:devices)
+                        1009 supriya:channel-strip:2 (session.mixers[0].tracks[0]:channel-strip)
+                            active: c5, bus: 18.0, gain: c6, gate: 1.0
+                        1011 supriya:meters:2 (session.mixers[0].tracks[0]:output-levels)
+                            in_: 18.0, out: 9.0
+                        1012 supriya:patch-cable:2x2 (session.mixers[0].tracks[0].output:synth)
+                            active: c5, gain: 0.0, gate: 1.0, in_: 18.0, out: 16.0
+                1004 supriya:meters:2 (session.mixers[0]:input-levels)
+                    in_: 16.0, out: 1.0
+                1002 group (session.mixers[0]:devices)
+                1003 supriya:channel-strip:2 (session.mixers[0]:channel-strip)
+                    active: 1.0, bus: 16.0, gain: c0, gate: 1.0
+                1005 supriya:meters:2 (session.mixers[0]:output-levels)
+                    in_: 16.0, out: 3.0
+                1013 supriya:patch-cable:2x2 (session.mixers[0].output:synth)
+                    active: 1.0, gain: 0.0, gate: 1.0, in_: 16.0, out: 0.0
+            NODE TREE 1014 group (session.mixers[1]:group)
+                1015 group (session.mixers[1]:tracks)
+                    1020 group (session.mixers[1].tracks[0]:group)
+                        1021 group (session.mixers[1].tracks[0]:tracks)
+                        1024 supriya:meters:2 (session.mixers[1].tracks[0]:input-levels)
+                            in_: 22.0, out: 18.0
+                        1022 group (session.mixers[1].tracks[0]:devices)
+                        1023 supriya:channel-strip:2 (session.mixers[1].tracks[0]:channel-strip)
+                            active: c16, bus: 22.0, gain: c17, gate: 1.0
+                        1025 supriya:meters:2 (session.mixers[1].tracks[0]:output-levels)
+                            in_: 22.0, out: 20.0
+                        1026 supriya:patch-cable:2x2 (session.mixers[1].tracks[0].output:synth)
+                            active: c16, gain: 0.0, gate: 1.0, in_: 22.0, out: 20.0
+                1018 supriya:meters:2 (session.mixers[1]:input-levels)
+                    in_: 20.0, out: 12.0
+                1016 group (session.mixers[1]:devices)
+                1017 supriya:channel-strip:2 (session.mixers[1]:channel-strip)
+                    active: 1.0, bus: 20.0, gain: c11, gate: 1.0
+                1019 supriya:meters:2 (session.mixers[1]:output-levels)
+                    in_: 20.0, out: 14.0
+                1027 supriya:patch-cable:2x2 (session.mixers[1].output:synth)
+                    active: 1.0, gain: 0.0, gate: 1.0, in_: 20.0, out: 0.0
+        <session.contexts[1]>
+        """,
+    )
diff --git a/tests/mixers/test_Track.py b/tests/mixers/test_Track.py
new file mode 100644
index 000000000..a306a6074
--- /dev/null
+++ b/tests/mixers/test_Track.py
@@ -0,0 +1,1525 @@
+from typing import Dict, List, Optional, Union
+
+import pytest
+
+from supriya import OscBundle, OscMessage
+from supriya.mixers import Session
+from supriya.mixers.mixers import Mixer
+from supriya.mixers.synthdefs import DEVICE_DC_TESTER_2
+from supriya.mixers.tracks import Track, TrackContainer
+from supriya.typing import DEFAULT, Default
+
+from .conftest import assert_diff, capture, debug_tree, does_not_raise
+
+
+@pytest.mark.parametrize("online", [False, True])
+@pytest.mark.parametrize(
+    "expected_commands, expected_diff",
+    [
+        (
+            [
+                OscMessage("/d_recv", DEVICE_DC_TESTER_2.compile()),
+                OscMessage("/sync", 2),
+                OscBundle(
+                    contents=(
+                        OscMessage("/g_new", 1014, 1, 1008),
+                        OscMessage(
+                            "/s_new", "supriya:device-dc-tester:2", 1015, 1, 1014
+                        ),
+                    ),
+                ),
+            ],
+            """
+            --- initial
+            +++ mutation
+            @@ -6,6 +6,9 @@
+                             1010 supriya:meters:2 (session.mixers[0].tracks[0]:input-levels)
+                                 in_: 18.0, out: 7.0
+                             1008 group (session.mixers[0].tracks[0]:devices)
+            +                    1014 group (session.mixers[0].tracks[0].devices[0]:group)
+            +                        1015 supriya:device-dc-tester:2 (session.mixers[0].tracks[0].devices[0]:synth)
+            +                            dc: 1.0, out: 0.0
+                             1009 supriya:channel-strip:2 (session.mixers[0].tracks[0]:channel-strip)
+                                 active: c5, bus: 18.0, gain: c6, gate: 1.0
+                             1011 supriya:meters:2 (session.mixers[0].tracks[0]:output-levels)
+            """,
+        ),
+    ],
+)
+@pytest.mark.asyncio
+async def test_Track_add_device(
+    expected_commands: List[Union[OscBundle, OscMessage]],
+    expected_diff: str,
+    mixer: Mixer,
+    online: bool,
+    session: Session,
+    track: Track,
+) -> None:
+    # Pre-conditions
+    if online:
+        await session.boot()
+    # Operation
+    with capture(mixer.context) as commands:
+        device = await track.add_device()
+    # Post-conditions
+    assert device in track.devices
+    assert device.parent is track
+    assert track.devices[0] is device
+    if not online:
+        return
+    await assert_diff(
+        session,
+        expected_diff,
+        expected_initial_tree="""
+        <session.contexts[0]>
+            NODE TREE 1000 group (session.mixers[0]:group)
+                1001 group (session.mixers[0]:tracks)
+                    1006 group (session.mixers[0].tracks[0]:group)
+                        1007 group (session.mixers[0].tracks[0]:tracks)
+                        1010 supriya:meters:2 (session.mixers[0].tracks[0]:input-levels)
+                            in_: 18.0, out: 7.0
+                        1008 group (session.mixers[0].tracks[0]:devices)
+                        1009 supriya:channel-strip:2 (session.mixers[0].tracks[0]:channel-strip)
+                            active: c5, bus: 18.0, gain: c6, gate: 1.0
+                        1011 supriya:meters:2 (session.mixers[0].tracks[0]:output-levels)
+                            in_: 18.0, out: 9.0
+                        1012 supriya:patch-cable:2x2 (session.mixers[0].tracks[0].output:synth)
+                            active: c5, gain: 0.0, gate: 1.0, in_: 18.0, out: 16.0
+                1004 supriya:meters:2 (session.mixers[0]:input-levels)
+                    in_: 16.0, out: 1.0
+                1002 group (session.mixers[0]:devices)
+                1003 supriya:channel-strip:2 (session.mixers[0]:channel-strip)
+                    active: 1.0, bus: 16.0, gain: c0, gate: 1.0
+                1005 supriya:meters:2 (session.mixers[0]:output-levels)
+                    in_: 16.0, out: 3.0
+                1013 supriya:patch-cable:2x2 (session.mixers[0].output:synth)
+                    active: 1.0, gain: 0.0, gate: 1.0, in_: 16.0, out: 0.0
+        """,
+    )
+    assert commands == expected_commands
+
+
+@pytest.mark.parametrize("online", [False, True])
+@pytest.mark.parametrize(
+    "postfader, source, target, expected_commands, expected_diff",
+    [
+        (
+            True,
+            "self",
+            "mixer",
+            [
+                OscMessage(
+                    "/s_new",
+                    "supriya:patch-cable:2x2",
+                    1021,
+                    3,
+                    1009,
+                    "active",
+                    "c5",
+                    "in_",
+                    18.0,
+                    "out",
+                    16.0,
+                )
+            ],
+            """
+            --- initial
+            +++ mutation
+            @@ -8,6 +8,8 @@
+                             1008 group (session.mixers[0].tracks[0]:devices)
+                             1009 supriya:channel-strip:2 (session.mixers[0].tracks[0]:channel-strip)
+                                 active: c5, bus: 18.0, gain: c6, gate: 1.0
+            +                1021 supriya:patch-cable:2x2 (session.mixers[0].tracks[0].sends[0]:synth)
+            +                    active: c5, gain: 0.0, gate: 1.0, in_: 18.0, out: 16.0
+                             1011 supriya:meters:2 (session.mixers[0].tracks[0]:output-levels)
+                                 in_: 18.0, out: 9.0
+                             1012 supriya:patch-cable:2x2 (session.mixers[0].tracks[0].output:synth)
+            """,
+        ),
+        (
+            True,
+            "self",
+            "other",
+            [
+                OscMessage(
+                    "/s_new",
+                    "supriya:patch-cable:2x2",
+                    1021,
+                    3,
+                    1009,
+                    "active",
+                    "c5",
+                    "in_",
+                    18.0,
+                    "out",
+                    20.0,
+                )
+            ],
+            """
+            --- initial
+            +++ mutation
+            @@ -8,6 +8,8 @@
+                             1008 group (session.mixers[0].tracks[0]:devices)
+                             1009 supriya:channel-strip:2 (session.mixers[0].tracks[0]:channel-strip)
+                                 active: c5, bus: 18.0, gain: c6, gate: 1.0
+            +                1021 supriya:patch-cable:2x2 (session.mixers[0].tracks[0].sends[0]:synth)
+            +                    active: c5, gain: 0.0, gate: 1.0, in_: 18.0, out: 20.0
+                             1011 supriya:meters:2 (session.mixers[0].tracks[0]:output-levels)
+                                 in_: 18.0, out: 9.0
+                             1012 supriya:patch-cable:2x2 (session.mixers[0].tracks[0].output:synth)
+            """,
+        ),
+        (
+            False,
+            "self",
+            "other",
+            [
+                OscMessage(
+                    "/s_new",
+                    "supriya:patch-cable:2x2",
+                    1021,
+                    2,
+                    1009,
+                    "active",
+                    "c5",
+                    "in_",
+                    18.0,
+                    "out",
+                    20.0,
+                )
+            ],
+            """
+            --- initial
+            +++ mutation
+            @@ -6,6 +6,8 @@
+                             1010 supriya:meters:2 (session.mixers[0].tracks[0]:input-levels)
+                                 in_: 18.0, out: 7.0
+                             1008 group (session.mixers[0].tracks[0]:devices)
+            +                1021 supriya:patch-cable:2x2 (session.mixers[0].tracks[0].sends[0]:synth)
+            +                    active: c5, gain: 0.0, gate: 1.0, in_: 18.0, out: 20.0
+                             1009 supriya:channel-strip:2 (session.mixers[0].tracks[0]:channel-strip)
+                                 active: c5, bus: 18.0, gain: c6, gate: 1.0
+                             1011 supriya:meters:2 (session.mixers[0].tracks[0]:output-levels)
+            """,
+        ),
+        (
+            False,
+            "self",
+            "self",
+            [
+                OscMessage(
+                    "/s_new",
+                    "supriya:fb-patch-cable:2x2",
+                    1021,
+                    0,
+                    1006,
+                    "active",
+                    "c5",
+                    "in_",
+                    22.0,
+                    "out",
+                    18.0,
+                ),
+                OscMessage(
+                    "/s_new",
+                    "supriya:patch-cable:2x2",
+                    1022,
+                    2,
+                    1009,
+                    "active",
+                    "c5",
+                    "in_",
+                    18.0,
+                    "out",
+                    22.0,
+                ),
+            ],
+            """
+            --- initial
+            +++ mutation
+            @@ -2,10 +2,14 @@
+                 NODE TREE 1000 group (session.mixers[0]:group)
+                     1001 group (session.mixers[0]:tracks)
+                         1006 group (session.mixers[0].tracks[0]:group)
+            +                1021 supriya:fb-patch-cable:2x2 (session.mixers[0].tracks[0].feedback:synth)
+            +                    active: c5, gain: 0.0, gate: 1.0, in_: 22.0, out: 18.0
+                             1007 group (session.mixers[0].tracks[0]:tracks)
+                             1010 supriya:meters:2 (session.mixers[0].tracks[0]:input-levels)
+                                 in_: 18.0, out: 7.0
+                             1008 group (session.mixers[0].tracks[0]:devices)
+            +                1022 supriya:patch-cable:2x2 (session.mixers[0].tracks[0].sends[0]:synth)
+            +                    active: c5, gain: 0.0, gate: 1.0, in_: 18.0, out: 22.0
+                             1009 supriya:channel-strip:2 (session.mixers[0].tracks[0]:channel-strip)
+                                 active: c5, bus: 18.0, gain: c6, gate: 1.0
+                             1011 supriya:meters:2 (session.mixers[0].tracks[0]:output-levels)
+            """,
+        ),
+        (
+            True,
+            "other",
+            "self",
+            [
+                OscMessage(
+                    "/s_new",
+                    "supriya:fb-patch-cable:2x2",
+                    1021,
+                    0,
+                    1006,
+                    "active",
+                    "c5",
+                    "in_",
+                    22.0,
+                    "out",
+                    18.0,
+                ),
+                OscMessage(
+                    "/s_new",
+                    "supriya:patch-cable:2x2",
+                    1022,
+                    3,
+                    1017,
+                    "active",
+                    "c11",
+                    "in_",
+                    20.0,
+                    "out",
+                    22.0,
+                ),
+            ],
+            """
+            --- initial
+            +++ mutation
+            @@ -2,6 +2,8 @@
+                 NODE TREE 1000 group (session.mixers[0]:group)
+                     1001 group (session.mixers[0]:tracks)
+                         1006 group (session.mixers[0].tracks[0]:group)
+            +                1021 supriya:fb-patch-cable:2x2 (session.mixers[0].tracks[0].feedback:synth)
+            +                    active: c5, gain: 0.0, gate: 1.0, in_: 22.0, out: 18.0
+                             1007 group (session.mixers[0].tracks[0]:tracks)
+                             1010 supriya:meters:2 (session.mixers[0].tracks[0]:input-levels)
+                                 in_: 18.0, out: 7.0
+            @@ -19,6 +21,8 @@
+                             1016 group (session.mixers[0].tracks[1]:devices)
+                             1017 supriya:channel-strip:2 (session.mixers[0].tracks[1]:channel-strip)
+                                 active: c11, bus: 20.0, gain: c12, gate: 1.0
+            +                1022 supriya:patch-cable:2x2 (session.mixers[0].tracks[1].sends[0]:synth)
+            +                    active: c11, gain: 0.0, gate: 1.0, in_: 20.0, out: 22.0
+                             1019 supriya:meters:2 (session.mixers[0].tracks[1]:output-levels)
+                                 in_: 20.0, out: 15.0
+                             1020 supriya:patch-cable:2x2 (session.mixers[0].tracks[1].output:synth)
+            """,
+        ),
+    ],
+)
+@pytest.mark.asyncio
+async def test_Track_add_send(
+    expected_commands: List[Union[OscBundle, OscMessage]],
+    expected_diff: str,
+    mixer: Mixer,
+    online: bool,
+    postfader: bool,
+    session: Session,
+    source: str,
+    target: str,
+    track: Track,
+) -> None:
+    # Pre-conditions
+    if online:
+        await session.boot()
+    targets: Dict[str, TrackContainer] = {
+        "mixer": mixer,
+        "other": await mixer.add_track(),
+        "self": track,
+    }
+    source_ = targets[source]
+    target_ = targets[target]
+    assert isinstance(source_, Track)
+    if online:
+        await debug_tree(session)
+    # Operation
+    with capture(mixer.context) as commands:
+        send = await source_.add_send(postfader=postfader, target=target_)
+    # Post-conditions
+    assert send in source_.sends
+    assert send.parent is source_
+    assert send.postfader == postfader
+    assert send.target is target_
+    assert source_.sends[0] is send
+    if not online:
+        return
+    await assert_diff(
+        session,
+        expected_diff,
+        expected_initial_tree="""
+        <session.contexts[0]>
+            NODE TREE 1000 group (session.mixers[0]:group)
+                1001 group (session.mixers[0]:tracks)
+                    1006 group (session.mixers[0].tracks[0]:group)
+                        1007 group (session.mixers[0].tracks[0]:tracks)
+                        1010 supriya:meters:2 (session.mixers[0].tracks[0]:input-levels)
+                            in_: 18.0, out: 7.0
+                        1008 group (session.mixers[0].tracks[0]:devices)
+                        1009 supriya:channel-strip:2 (session.mixers[0].tracks[0]:channel-strip)
+                            active: c5, bus: 18.0, gain: c6, gate: 1.0
+                        1011 supriya:meters:2 (session.mixers[0].tracks[0]:output-levels)
+                            in_: 18.0, out: 9.0
+                        1012 supriya:patch-cable:2x2 (session.mixers[0].tracks[0].output:synth)
+                            active: c5, gain: 0.0, gate: 1.0, in_: 18.0, out: 16.0
+                    1014 group (session.mixers[0].tracks[1]:group)
+                        1015 group (session.mixers[0].tracks[1]:tracks)
+                        1018 supriya:meters:2 (session.mixers[0].tracks[1]:input-levels)
+                            in_: 20.0, out: 13.0
+                        1016 group (session.mixers[0].tracks[1]:devices)
+                        1017 supriya:channel-strip:2 (session.mixers[0].tracks[1]:channel-strip)
+                            active: c11, bus: 20.0, gain: c12, gate: 1.0
+                        1019 supriya:meters:2 (session.mixers[0].tracks[1]:output-levels)
+                            in_: 20.0, out: 15.0
+                        1020 supriya:patch-cable:2x2 (session.mixers[0].tracks[1].output:synth)
+                            active: c11, gain: 0.0, gate: 1.0, in_: 20.0, out: 16.0
+                1004 supriya:meters:2 (session.mixers[0]:input-levels)
+                    in_: 16.0, out: 1.0
+                1002 group (session.mixers[0]:devices)
+                1003 supriya:channel-strip:2 (session.mixers[0]:channel-strip)
+                    active: 1.0, bus: 16.0, gain: c0, gate: 1.0
+                1005 supriya:meters:2 (session.mixers[0]:output-levels)
+                    in_: 16.0, out: 3.0
+                1013 supriya:patch-cable:2x2 (session.mixers[0].output:synth)
+                    active: 1.0, gain: 0.0, gate: 1.0, in_: 16.0, out: 0.0
+        """,
+    )
+    assert commands == expected_commands
+
+
+@pytest.mark.parametrize("online", [False, True])
+@pytest.mark.asyncio
+async def test_Track_add_track(
+    mixer: Mixer,
+    online: bool,
+    session: Session,
+    track: Track,
+) -> None:
+    # Pre-conditions
+    if online:
+        await session.boot()
+    # Operation
+    with capture(mixer.context) as commands:
+        child_track = await track.add_track()
+    # Post-conditions
+    assert child_track in track.tracks
+    assert child_track.parent is track
+    assert track.tracks[0] is child_track
+    if not online:
+        return
+    await assert_diff(
+        session,
+        expected_diff="""
+        --- initial
+        +++ mutation
+        @@ -3,6 +3,17 @@
+                 1001 group (session.mixers[0]:tracks)
+                     1006 group (session.mixers[0].tracks[0]:group)
+                         1007 group (session.mixers[0].tracks[0]:tracks)
+        +                    1014 group (session.mixers[0].tracks[0].tracks[0]:group)
+        +                        1015 group (session.mixers[0].tracks[0].tracks[0]:tracks)
+        +                        1018 supriya:meters:2 (session.mixers[0].tracks[0].tracks[0]:input-levels)
+        +                            in_: 20.0, out: 13.0
+        +                        1016 group (session.mixers[0].tracks[0].tracks[0]:devices)
+        +                        1017 supriya:channel-strip:2 (session.mixers[0].tracks[0].tracks[0]:channel-strip)
+        +                            active: c11, bus: 20.0, gain: c12, gate: 1.0
+        +                        1019 supriya:meters:2 (session.mixers[0].tracks[0].tracks[0]:output-levels)
+        +                            in_: 20.0, out: 15.0
+        +                        1020 supriya:patch-cable:2x2 (session.mixers[0].tracks[0].tracks[0].output:synth)
+        +                            active: c11, gain: 0.0, gate: 1.0, in_: 20.0, out: 18.0
+                         1010 supriya:meters:2 (session.mixers[0].tracks[0]:input-levels)
+                             in_: 18.0, out: 7.0
+                         1008 group (session.mixers[0].tracks[0]:devices)
+        """,
+        expected_initial_tree="""
+        <session.contexts[0]>
+            NODE TREE 1000 group (session.mixers[0]:group)
+                1001 group (session.mixers[0]:tracks)
+                    1006 group (session.mixers[0].tracks[0]:group)
+                        1007 group (session.mixers[0].tracks[0]:tracks)
+                        1010 supriya:meters:2 (session.mixers[0].tracks[0]:input-levels)
+                            in_: 18.0, out: 7.0
+                        1008 group (session.mixers[0].tracks[0]:devices)
+                        1009 supriya:channel-strip:2 (session.mixers[0].tracks[0]:channel-strip)
+                            active: c5, bus: 18.0, gain: c6, gate: 1.0
+                        1011 supriya:meters:2 (session.mixers[0].tracks[0]:output-levels)
+                            in_: 18.0, out: 9.0
+                        1012 supriya:patch-cable:2x2 (session.mixers[0].tracks[0].output:synth)
+                            active: c5, gain: 0.0, gate: 1.0, in_: 18.0, out: 16.0
+                1004 supriya:meters:2 (session.mixers[0]:input-levels)
+                    in_: 16.0, out: 1.0
+                1002 group (session.mixers[0]:devices)
+                1003 supriya:channel-strip:2 (session.mixers[0]:channel-strip)
+                    active: 1.0, bus: 16.0, gain: c0, gate: 1.0
+                1005 supriya:meters:2 (session.mixers[0]:output-levels)
+                    in_: 16.0, out: 3.0
+                1013 supriya:patch-cable:2x2 (session.mixers[0].output:synth)
+                    active: 1.0, gain: 0.0, gate: 1.0, in_: 16.0, out: 0.0
+        """,
+    )
+    assert commands == [
+        OscBundle(
+            contents=(
+                OscMessage("/c_set", 11, 1.0, 12, 0.0),
+                OscMessage("/c_fill", 13, 2, 0.0, 15, 2, 0.0),
+                OscMessage("/g_new", 1014, 1, 1007, 1015, 0, 1014, 1016, 1, 1014),
+                OscMessage(
+                    "/s_new",
+                    "supriya:channel-strip:2",
+                    1017,
+                    1,
+                    1014,
+                    "active",
+                    "c11",
+                    "bus",
+                    20.0,
+                    "gain",
+                    "c12",
+                ),
+                OscMessage(
+                    "/s_new",
+                    "supriya:meters:2",
+                    1018,
+                    3,
+                    1015,
+                    "in_",
+                    20.0,
+                    "out",
+                    13.0,
+                ),
+                OscMessage(
+                    "/s_new",
+                    "supriya:meters:2",
+                    1019,
+                    3,
+                    1017,
+                    "in_",
+                    20.0,
+                    "out",
+                    15.0,
+                ),
+            ),
+        ),
+        OscMessage(
+            "/s_new",
+            "supriya:patch-cable:2x2",
+            1020,
+            1,
+            1014,
+            "active",
+            "c11",
+            "in_",
+            20.0,
+            "out",
+            18.0,
+        ),
+    ]
+
+
+@pytest.mark.xfail
+@pytest.mark.parametrize("online", [False, True])
+@pytest.mark.parametrize(
+    "target, expected_commands, expected_diff",
+    [
+        ("parent", [], ""),
+        ("self", [], ""),
+        ("child", [], ""),
+        ("sibling", [], ""),
+    ],
+)
+@pytest.mark.asyncio
+async def test_Track_delete(
+    expected_commands: List[Union[OscBundle, OscMessage]],
+    expected_diff: str,
+    online: bool,
+    mixer: Mixer,
+    session: Session,
+    target: str,
+) -> None:
+    # Pre-conditions
+    if online:
+        await session.boot()
+    targets: Dict[str, Track] = {
+        "parent": (parent := await mixer.add_track()),
+        "self": (track := await parent.add_track()),
+        "child": await track.add_track(),
+        "sibling": (sibling := await mixer.add_track()),
+    }
+    await sibling.set_output(track)
+    target_ = targets[target]
+    parent_ = target_.parent
+    # Operation
+    with capture(mixer.context) as commands:
+        await target_.delete()
+    # Post-conditions
+    assert parent_ and target_ not in parent_.children
+    if not online:
+        raise Exception
+    await assert_diff(
+        session,
+        expected_diff,
+        expected_initial_tree="""
+        """,
+    )
+    assert commands == expected_commands
+    raise Exception
+
+
+@pytest.mark.parametrize("online", [False, True])
+@pytest.mark.parametrize(
+    "parent, index, maybe_raises, expected_graph_order, expected_diff, expected_commands",
+    [
+        ("self", 0, pytest.raises(RuntimeError), (0, 0), "", []),
+        ("mixer", 0, does_not_raise, (0, 0), "", []),
+        (
+            "mixer",
+            1,
+            does_not_raise,
+            (0, 1),
+            """
+            --- initial
+            +++ mutation
+            @@ -1,30 +1,30 @@
+             <session.contexts[0]>
+                 NODE TREE 1000 group (session.mixers[0]:group)
+                     1001 group (session.mixers[0]:tracks)
+            -            1006 group (session.mixers[0].tracks[0]:group)
+            -                1007 group (session.mixers[0].tracks[0]:tracks)
+            -                1010 supriya:meters:2 (session.mixers[0].tracks[0]:input-levels)
+            +            1014 group (session.mixers[0].tracks[0]:group)
+            +                1015 group (session.mixers[0].tracks[0]:tracks)
+            +                1018 supriya:meters:2 (session.mixers[0].tracks[0]:input-levels)
+            +                    in_: 20.0, out: 13.0
+            +                1016 group (session.mixers[0].tracks[0]:devices)
+            +                1017 supriya:channel-strip:2 (session.mixers[0].tracks[0]:channel-strip)
+            +                    active: c11, bus: 20.0, gain: c12, gate: 1.0
+            +                1019 supriya:meters:2 (session.mixers[0].tracks[0]:output-levels)
+            +                    in_: 20.0, out: 15.0
+            +                1020 supriya:patch-cable:2x2 (session.mixers[0].tracks[0].output:synth)
+            +                    active: c11, gain: 0.0, gate: 1.0, in_: 20.0, out: 16.0
+            +            1006 group (session.mixers[0].tracks[1]:group)
+            +                1007 group (session.mixers[0].tracks[1]:tracks)
+            +                1010 supriya:meters:2 (session.mixers[0].tracks[1]:input-levels)
+                                 in_: 18.0, out: 7.0
+            -                1008 group (session.mixers[0].tracks[0]:devices)
+            -                1009 supriya:channel-strip:2 (session.mixers[0].tracks[0]:channel-strip)
+            +                1008 group (session.mixers[0].tracks[1]:devices)
+            +                1009 supriya:channel-strip:2 (session.mixers[0].tracks[1]:channel-strip)
+                                 active: c5, bus: 18.0, gain: c6, gate: 1.0
+            -                1042 supriya:patch-cable:2x2 (session.mixers[0].tracks[0].sends[0]:synth)
+            +                1042 supriya:patch-cable:2x2 (session.mixers[0].tracks[1].sends[0]:synth)
+                                 active: c5, gain: 0.0, gate: 1.0, in_: 18.0, out: 22.0
+            -                1011 supriya:meters:2 (session.mixers[0].tracks[0]:output-levels)
+            +                1011 supriya:meters:2 (session.mixers[0].tracks[1]:output-levels)
+                                 in_: 18.0, out: 9.0
+            -                1012 supriya:patch-cable:2x2 (session.mixers[0].tracks[0].output:synth)
+            +                1012 supriya:patch-cable:2x2 (session.mixers[0].tracks[1].output:synth)
+                                 active: c5, gain: 0.0, gate: 1.0, in_: 18.0, out: 16.0
+            -            1014 group (session.mixers[0].tracks[1]:group)
+            -                1015 group (session.mixers[0].tracks[1]:tracks)
+            -                1018 supriya:meters:2 (session.mixers[0].tracks[1]:input-levels)
+            -                    in_: 20.0, out: 13.0
+            -                1016 group (session.mixers[0].tracks[1]:devices)
+            -                1017 supriya:channel-strip:2 (session.mixers[0].tracks[1]:channel-strip)
+            -                    active: c11, bus: 20.0, gain: c12, gate: 1.0
+            -                1019 supriya:meters:2 (session.mixers[0].tracks[1]:output-levels)
+            -                    in_: 20.0, out: 15.0
+            -                1020 supriya:patch-cable:2x2 (session.mixers[0].tracks[1].output:synth)
+            -                    active: c11, gain: 0.0, gate: 1.0, in_: 20.0, out: 16.0
+                         1021 group (session.mixers[0].tracks[2]:group)
+                             1022 group (session.mixers[0].tracks[2]:tracks)
+                             1025 supriya:meters:2 (session.mixers[0].tracks[2]:input-levels)
+            """,
+            [OscMessage("/n_after", 1006, 1014)],
+        ),
+        (
+            "mixer",
+            2,
+            does_not_raise,
+            (0, 2),
+            """
+            --- initial
+            +++ mutation
+            @@ -1,41 +1,45 @@
+             <session.contexts[0]>
+                 NODE TREE 1000 group (session.mixers[0]:group)
+                     1001 group (session.mixers[0]:tracks)
+            -            1006 group (session.mixers[0].tracks[0]:group)
+            -                1007 group (session.mixers[0].tracks[0]:tracks)
+            -                1010 supriya:meters:2 (session.mixers[0].tracks[0]:input-levels)
+            +            1014 group (session.mixers[0].tracks[0]:group)
+            +                1015 group (session.mixers[0].tracks[0]:tracks)
+            +                1018 supriya:meters:2 (session.mixers[0].tracks[0]:input-levels)
+            +                    in_: 20.0, out: 13.0
+            +                1016 group (session.mixers[0].tracks[0]:devices)
+            +                1017 supriya:channel-strip:2 (session.mixers[0].tracks[0]:channel-strip)
+            +                    active: c11, bus: 20.0, gain: c12, gate: 1.0
+            +                1019 supriya:meters:2 (session.mixers[0].tracks[0]:output-levels)
+            +                    in_: 20.0, out: 15.0
+            +                1020 supriya:patch-cable:2x2 (session.mixers[0].tracks[0].output:synth)
+            +                    active: c11, gain: 0.0, gate: 1.0, in_: 20.0, out: 16.0
+            +            1021 group (session.mixers[0].tracks[1]:group)
+            +                1043 supriya:fb-patch-cable:2x2 (session.mixers[0].tracks[1].feedback:synth)
+            +                    active: c17, gain: 0.0, gate: 1.0, in_: 28.0, out: 22.0
+            +                1022 group (session.mixers[0].tracks[1]:tracks)
+            +                1025 supriya:meters:2 (session.mixers[0].tracks[1]:input-levels)
+            +                    in_: 22.0, out: 19.0
+            +                1023 group (session.mixers[0].tracks[1]:devices)
+            +                1024 supriya:channel-strip:2 (session.mixers[0].tracks[1]:channel-strip)
+            +                    active: c17, bus: 22.0, gain: c18, gate: 1.0
+            +                1026 supriya:meters:2 (session.mixers[0].tracks[1]:output-levels)
+            +                    in_: 22.0, out: 21.0
+            +                1027 supriya:patch-cable:2x2 (session.mixers[0].tracks[1].output:synth)
+            +                    active: c17, gain: 0.0, gate: 1.0, in_: 22.0, out: 16.0
+            +            1006 group (session.mixers[0].tracks[2]:group)
+            +                1007 group (session.mixers[0].tracks[2]:tracks)
+            +                1010 supriya:meters:2 (session.mixers[0].tracks[2]:input-levels)
+                                 in_: 18.0, out: 7.0
+            -                1008 group (session.mixers[0].tracks[0]:devices)
+            -                1009 supriya:channel-strip:2 (session.mixers[0].tracks[0]:channel-strip)
+            +                1008 group (session.mixers[0].tracks[2]:devices)
+            +                1009 supriya:channel-strip:2 (session.mixers[0].tracks[2]:channel-strip)
+                                 active: c5, bus: 18.0, gain: c6, gate: 1.0
+            -                1042 supriya:patch-cable:2x2 (session.mixers[0].tracks[0].sends[0]:synth)
+            -                    active: c5, gain: 0.0, gate: 1.0, in_: 18.0, out: 22.0
+            -                1011 supriya:meters:2 (session.mixers[0].tracks[0]:output-levels)
+            +                1044 supriya:patch-cable:2x2 (session.mixers[0].tracks[2].sends[0]:synth)
+            +                    active: c5, gain: 0.0, gate: 1.0, in_: 18.0, out: 28.0
+            +                1042 supriya:patch-cable:2x2
+            +                    active: c5, gain: 0.0, gate: 0.0, in_: 18.0, out: 22.0
+            +                1011 supriya:meters:2 (session.mixers[0].tracks[2]:output-levels)
+                                 in_: 18.0, out: 9.0
+            -                1012 supriya:patch-cable:2x2 (session.mixers[0].tracks[0].output:synth)
+            +                1012 supriya:patch-cable:2x2 (session.mixers[0].tracks[2].output:synth)
+                                 active: c5, gain: 0.0, gate: 1.0, in_: 18.0, out: 16.0
+            -            1014 group (session.mixers[0].tracks[1]:group)
+            -                1015 group (session.mixers[0].tracks[1]:tracks)
+            -                1018 supriya:meters:2 (session.mixers[0].tracks[1]:input-levels)
+            -                    in_: 20.0, out: 13.0
+            -                1016 group (session.mixers[0].tracks[1]:devices)
+            -                1017 supriya:channel-strip:2 (session.mixers[0].tracks[1]:channel-strip)
+            -                    active: c11, bus: 20.0, gain: c12, gate: 1.0
+            -                1019 supriya:meters:2 (session.mixers[0].tracks[1]:output-levels)
+            -                    in_: 20.0, out: 15.0
+            -                1020 supriya:patch-cable:2x2 (session.mixers[0].tracks[1].output:synth)
+            -                    active: c11, gain: 0.0, gate: 1.0, in_: 20.0, out: 16.0
+            -            1021 group (session.mixers[0].tracks[2]:group)
+            -                1022 group (session.mixers[0].tracks[2]:tracks)
+            -                1025 supriya:meters:2 (session.mixers[0].tracks[2]:input-levels)
+            -                    in_: 22.0, out: 19.0
+            -                1023 group (session.mixers[0].tracks[2]:devices)
+            -                1024 supriya:channel-strip:2 (session.mixers[0].tracks[2]:channel-strip)
+            -                    active: c17, bus: 22.0, gain: c18, gate: 1.0
+            -                1026 supriya:meters:2 (session.mixers[0].tracks[2]:output-levels)
+            -                    in_: 22.0, out: 21.0
+            -                1027 supriya:patch-cable:2x2 (session.mixers[0].tracks[2].output:synth)
+            -                    active: c17, gain: 0.0, gate: 1.0, in_: 22.0, out: 16.0
+                     1004 supriya:meters:2 (session.mixers[0]:input-levels)
+                         in_: 16.0, out: 1.0
+                     1002 group (session.mixers[0]:devices)
+            """,
+            [
+                OscMessage("/n_after", 1006, 1021),
+                OscMessage(
+                    "/s_new",
+                    "supriya:fb-patch-cable:2x2",
+                    1043,
+                    0,
+                    1021,
+                    "active",
+                    "c17",
+                    "in_",
+                    28.0,
+                    "out",
+                    22.0,
+                ),
+                OscBundle(
+                    contents=(
+                        OscMessage("/n_set", 1042, "gate", 0.0),
+                        OscMessage(
+                            "/s_new",
+                            "supriya:patch-cable:2x2",
+                            1044,
+                            3,
+                            1009,
+                            "active",
+                            "c5",
+                            "in_",
+                            18.0,
+                            "out",
+                            28.0,
+                        ),
+                    ),
+                ),
+            ],
+        ),
+        (
+            "other",
+            0,
+            does_not_raise,
+            (0, 0, 2),
+            """
+            --- initial
+            +++ mutation
+            @@ -1,40 +1,42 @@
+             <session.contexts[0]>
+                 NODE TREE 1000 group (session.mixers[0]:group)
+                     1001 group (session.mixers[0]:tracks)
+            -            1006 group (session.mixers[0].tracks[0]:group)
+            -                1007 group (session.mixers[0].tracks[0]:tracks)
+            -                1010 supriya:meters:2 (session.mixers[0].tracks[0]:input-levels)
+            -                    in_: 18.0, out: 7.0
+            -                1008 group (session.mixers[0].tracks[0]:devices)
+            -                1009 supriya:channel-strip:2 (session.mixers[0].tracks[0]:channel-strip)
+            -                    active: c5, bus: 18.0, gain: c6, gate: 1.0
+            -                1042 supriya:patch-cable:2x2 (session.mixers[0].tracks[0].sends[0]:synth)
+            -                    active: c5, gain: 0.0, gate: 1.0, in_: 18.0, out: 22.0
+            -                1011 supriya:meters:2 (session.mixers[0].tracks[0]:output-levels)
+            -                    in_: 18.0, out: 9.0
+            -                1012 supriya:patch-cable:2x2 (session.mixers[0].tracks[0].output:synth)
+            -                    active: c5, gain: 0.0, gate: 1.0, in_: 18.0, out: 16.0
+            -            1014 group (session.mixers[0].tracks[1]:group)
+            -                1015 group (session.mixers[0].tracks[1]:tracks)
+            -                1018 supriya:meters:2 (session.mixers[0].tracks[1]:input-levels)
+            +            1014 group (session.mixers[0].tracks[0]:group)
+            +                1015 group (session.mixers[0].tracks[0]:tracks)
+            +                    1006 group (session.mixers[0].tracks[0].tracks[0]:group)
+            +                        1007 group (session.mixers[0].tracks[0].tracks[0]:tracks)
+            +                        1010 supriya:meters:2 (session.mixers[0].tracks[0].tracks[0]:input-levels)
+            +                            in_: 18.0, out: 7.0
+            +                        1008 group (session.mixers[0].tracks[0].tracks[0]:devices)
+            +                        1009 supriya:channel-strip:2 (session.mixers[0].tracks[0].tracks[0]:channel-strip)
+            +                            active: c5, bus: 18.0, gain: c6, gate: 1.0
+            +                        1042 supriya:patch-cable:2x2 (session.mixers[0].tracks[0].tracks[0].sends[0]:synth)
+            +                            active: c5, gain: 0.0, gate: 1.0, in_: 18.0, out: 22.0
+            +                        1011 supriya:meters:2 (session.mixers[0].tracks[0].tracks[0]:output-levels)
+            +                            in_: 18.0, out: 9.0
+            +                        1012 supriya:patch-cable:2x2
+            +                            active: c5, gain: 0.0, gate: 0.0, in_: 18.0, out: 16.0
+            +                        1043 supriya:patch-cable:2x2 (session.mixers[0].tracks[0].tracks[0].output:synth)
+            +                            active: c5, gain: 0.0, gate: 1.0, in_: 18.0, out: 20.0
+            +                1018 supriya:meters:2 (session.mixers[0].tracks[0]:input-levels)
+                                 in_: 20.0, out: 13.0
+            -                1016 group (session.mixers[0].tracks[1]:devices)
+            -                1017 supriya:channel-strip:2 (session.mixers[0].tracks[1]:channel-strip)
+            +                1016 group (session.mixers[0].tracks[0]:devices)
+            +                1017 supriya:channel-strip:2 (session.mixers[0].tracks[0]:channel-strip)
+                                 active: c11, bus: 20.0, gain: c12, gate: 1.0
+            -                1019 supriya:meters:2 (session.mixers[0].tracks[1]:output-levels)
+            +                1019 supriya:meters:2 (session.mixers[0].tracks[0]:output-levels)
+                                 in_: 20.0, out: 15.0
+            -                1020 supriya:patch-cable:2x2 (session.mixers[0].tracks[1].output:synth)
+            +                1020 supriya:patch-cable:2x2 (session.mixers[0].tracks[0].output:synth)
+                                 active: c11, gain: 0.0, gate: 1.0, in_: 20.0, out: 16.0
+            -            1021 group (session.mixers[0].tracks[2]:group)
+            -                1022 group (session.mixers[0].tracks[2]:tracks)
+            -                1025 supriya:meters:2 (session.mixers[0].tracks[2]:input-levels)
+            +            1021 group (session.mixers[0].tracks[1]:group)
+            +                1022 group (session.mixers[0].tracks[1]:tracks)
+            +                1025 supriya:meters:2 (session.mixers[0].tracks[1]:input-levels)
+                                 in_: 22.0, out: 19.0
+            -                1023 group (session.mixers[0].tracks[2]:devices)
+            -                1024 supriya:channel-strip:2 (session.mixers[0].tracks[2]:channel-strip)
+            +                1023 group (session.mixers[0].tracks[1]:devices)
+            +                1024 supriya:channel-strip:2 (session.mixers[0].tracks[1]:channel-strip)
+                                 active: c17, bus: 22.0, gain: c18, gate: 1.0
+            -                1026 supriya:meters:2 (session.mixers[0].tracks[2]:output-levels)
+            +                1026 supriya:meters:2 (session.mixers[0].tracks[1]:output-levels)
+                                 in_: 22.0, out: 21.0
+            -                1027 supriya:patch-cable:2x2 (session.mixers[0].tracks[2].output:synth)
+            +                1027 supriya:patch-cable:2x2 (session.mixers[0].tracks[1].output:synth)
+                                 active: c17, gain: 0.0, gate: 1.0, in_: 22.0, out: 16.0
+                     1004 supriya:meters:2 (session.mixers[0]:input-levels)
+                         in_: 16.0, out: 1.0
+            """,
+            [
+                OscMessage("/g_head", 1015, 1006),
+                OscBundle(
+                    contents=(
+                        OscMessage("/n_set", 1012, "gate", 0.0),
+                        OscMessage(
+                            "/s_new",
+                            "supriya:patch-cable:2x2",
+                            1043,
+                            1,
+                            1006,
+                            "active",
+                            "c5",
+                            "in_",
+                            18.0,
+                            "out",
+                            20.0,
+                        ),
+                    ),
+                ),
+            ],
+        ),
+        (
+            "other_other",
+            0,
+            does_not_raise,
+            (0, 1, 2),
+            """
+            --- initial
+            +++ mutation
+            @@ -1,40 +1,42 @@
+             <session.contexts[0]>
+                 NODE TREE 1000 group (session.mixers[0]:group)
+                     1001 group (session.mixers[0]:tracks)
+            -            1006 group (session.mixers[0].tracks[0]:group)
+            -                1007 group (session.mixers[0].tracks[0]:tracks)
+            -                1010 supriya:meters:2 (session.mixers[0].tracks[0]:input-levels)
+            -                    in_: 18.0, out: 7.0
+            -                1008 group (session.mixers[0].tracks[0]:devices)
+            -                1009 supriya:channel-strip:2 (session.mixers[0].tracks[0]:channel-strip)
+            -                    active: c5, bus: 18.0, gain: c6, gate: 1.0
+            -                1042 supriya:patch-cable:2x2 (session.mixers[0].tracks[0].sends[0]:synth)
+            -                    active: c5, gain: 0.0, gate: 1.0, in_: 18.0, out: 22.0
+            -                1011 supriya:meters:2 (session.mixers[0].tracks[0]:output-levels)
+            -                    in_: 18.0, out: 9.0
+            -                1012 supriya:patch-cable:2x2 (session.mixers[0].tracks[0].output:synth)
+            -                    active: c5, gain: 0.0, gate: 1.0, in_: 18.0, out: 16.0
+            -            1014 group (session.mixers[0].tracks[1]:group)
+            -                1015 group (session.mixers[0].tracks[1]:tracks)
+            -                1018 supriya:meters:2 (session.mixers[0].tracks[1]:input-levels)
+            +            1014 group (session.mixers[0].tracks[0]:group)
+            +                1015 group (session.mixers[0].tracks[0]:tracks)
+            +                1018 supriya:meters:2 (session.mixers[0].tracks[0]:input-levels)
+                                 in_: 20.0, out: 13.0
+            -                1016 group (session.mixers[0].tracks[1]:devices)
+            -                1017 supriya:channel-strip:2 (session.mixers[0].tracks[1]:channel-strip)
+            +                1016 group (session.mixers[0].tracks[0]:devices)
+            +                1017 supriya:channel-strip:2 (session.mixers[0].tracks[0]:channel-strip)
+                                 active: c11, bus: 20.0, gain: c12, gate: 1.0
+            -                1019 supriya:meters:2 (session.mixers[0].tracks[1]:output-levels)
+            +                1019 supriya:meters:2 (session.mixers[0].tracks[0]:output-levels)
+                                 in_: 20.0, out: 15.0
+            -                1020 supriya:patch-cable:2x2 (session.mixers[0].tracks[1].output:synth)
+            +                1020 supriya:patch-cable:2x2 (session.mixers[0].tracks[0].output:synth)
+                                 active: c11, gain: 0.0, gate: 1.0, in_: 20.0, out: 16.0
+            -            1021 group (session.mixers[0].tracks[2]:group)
+            -                1022 group (session.mixers[0].tracks[2]:tracks)
+            -                1025 supriya:meters:2 (session.mixers[0].tracks[2]:input-levels)
+            +            1021 group (session.mixers[0].tracks[1]:group)
+            +                1022 group (session.mixers[0].tracks[1]:tracks)
+            +                    1006 group (session.mixers[0].tracks[1].tracks[0]:group)
+            +                        1007 group (session.mixers[0].tracks[1].tracks[0]:tracks)
+            +                        1010 supriya:meters:2 (session.mixers[0].tracks[1].tracks[0]:input-levels)
+            +                            in_: 18.0, out: 7.0
+            +                        1008 group (session.mixers[0].tracks[1].tracks[0]:devices)
+            +                        1009 supriya:channel-strip:2 (session.mixers[0].tracks[1].tracks[0]:channel-strip)
+            +                            active: c5, bus: 18.0, gain: c6, gate: 1.0
+            +                        1042 supriya:patch-cable:2x2 (session.mixers[0].tracks[1].tracks[0].sends[0]:synth)
+            +                            active: c5, gain: 0.0, gate: 1.0, in_: 18.0, out: 22.0
+            +                        1011 supriya:meters:2 (session.mixers[0].tracks[1].tracks[0]:output-levels)
+            +                            in_: 18.0, out: 9.0
+            +                        1012 supriya:patch-cable:2x2
+            +                            active: c5, gain: 0.0, gate: 0.0, in_: 18.0, out: 16.0
+            +                        1043 supriya:patch-cable:2x2 (session.mixers[0].tracks[1].tracks[0].output:synth)
+            +                            active: c5, gain: 0.0, gate: 1.0, in_: 18.0, out: 22.0
+            +                1025 supriya:meters:2 (session.mixers[0].tracks[1]:input-levels)
+                                 in_: 22.0, out: 19.0
+            -                1023 group (session.mixers[0].tracks[2]:devices)
+            -                1024 supriya:channel-strip:2 (session.mixers[0].tracks[2]:channel-strip)
+            +                1023 group (session.mixers[0].tracks[1]:devices)
+            +                1024 supriya:channel-strip:2 (session.mixers[0].tracks[1]:channel-strip)
+                                 active: c17, bus: 22.0, gain: c18, gate: 1.0
+            -                1026 supriya:meters:2 (session.mixers[0].tracks[2]:output-levels)
+            +                1026 supriya:meters:2 (session.mixers[0].tracks[1]:output-levels)
+                                 in_: 22.0, out: 21.0
+            -                1027 supriya:patch-cable:2x2 (session.mixers[0].tracks[2].output:synth)
+            +                1027 supriya:patch-cable:2x2 (session.mixers[0].tracks[1].output:synth)
+                                 active: c17, gain: 0.0, gate: 1.0, in_: 22.0, out: 16.0
+                     1004 supriya:meters:2 (session.mixers[0]:input-levels)
+                         in_: 16.0, out: 1.0
+            """,
+            [
+                OscMessage("/g_head", 1022, 1006),
+                OscBundle(
+                    contents=(
+                        OscMessage("/n_set", 1012, "gate", 0.0),
+                        OscMessage(
+                            "/s_new",
+                            "supriya:patch-cable:2x2",
+                            1043,
+                            1,
+                            1006,
+                            "active",
+                            "c5",
+                            "in_",
+                            18.0,
+                            "out",
+                            22.0,
+                        ),
+                    ),
+                ),
+            ],
+        ),
+        ("other_mixer", 0, pytest.raises(RuntimeError), (0, 0), "", []),
+    ],
+)
+@pytest.mark.asyncio
+async def test_Track_move(
+    expected_commands: List[Union[OscBundle, OscMessage]],
+    expected_graph_order: List[int],
+    expected_diff: str,
+    index: int,
+    mixer: Mixer,
+    online: bool,
+    parent: str,
+    maybe_raises,
+    session: Session,
+    track: Track,
+) -> None:
+    # Pre-conditions
+    print("Pre-conditions")
+    if online:
+        await session.boot()
+    targets: Dict[str, TrackContainer] = {
+        "self": track,
+        "mixer": mixer,
+        "other": await mixer.add_track(),
+        "other_other": (other_other := await mixer.add_track()),
+        "other_mixer": await session.add_mixer(),
+    }
+    await track.add_send(target=other_other)
+    if online:
+        await debug_tree(session)
+    # Operation
+    print("Operation")
+    with maybe_raises, capture(mixer.context) as commands:
+        await track.move(index=index, parent=targets[parent])
+    # Post-conditions
+    print("Post-conditions")
+    assert track.graph_order == expected_graph_order
+    if not online:
+        return
+    await assert_diff(
+        session,
+        expected_diff,
+        expected_initial_tree="""
+        <session.contexts[0]>
+            NODE TREE 1000 group (session.mixers[0]:group)
+                1001 group (session.mixers[0]:tracks)
+                    1006 group (session.mixers[0].tracks[0]:group)
+                        1007 group (session.mixers[0].tracks[0]:tracks)
+                        1010 supriya:meters:2 (session.mixers[0].tracks[0]:input-levels)
+                            in_: 18.0, out: 7.0
+                        1008 group (session.mixers[0].tracks[0]:devices)
+                        1009 supriya:channel-strip:2 (session.mixers[0].tracks[0]:channel-strip)
+                            active: c5, bus: 18.0, gain: c6, gate: 1.0
+                        1042 supriya:patch-cable:2x2 (session.mixers[0].tracks[0].sends[0]:synth)
+                            active: c5, gain: 0.0, gate: 1.0, in_: 18.0, out: 22.0
+                        1011 supriya:meters:2 (session.mixers[0].tracks[0]:output-levels)
+                            in_: 18.0, out: 9.0
+                        1012 supriya:patch-cable:2x2 (session.mixers[0].tracks[0].output:synth)
+                            active: c5, gain: 0.0, gate: 1.0, in_: 18.0, out: 16.0
+                    1014 group (session.mixers[0].tracks[1]:group)
+                        1015 group (session.mixers[0].tracks[1]:tracks)
+                        1018 supriya:meters:2 (session.mixers[0].tracks[1]:input-levels)
+                            in_: 20.0, out: 13.0
+                        1016 group (session.mixers[0].tracks[1]:devices)
+                        1017 supriya:channel-strip:2 (session.mixers[0].tracks[1]:channel-strip)
+                            active: c11, bus: 20.0, gain: c12, gate: 1.0
+                        1019 supriya:meters:2 (session.mixers[0].tracks[1]:output-levels)
+                            in_: 20.0, out: 15.0
+                        1020 supriya:patch-cable:2x2 (session.mixers[0].tracks[1].output:synth)
+                            active: c11, gain: 0.0, gate: 1.0, in_: 20.0, out: 16.0
+                    1021 group (session.mixers[0].tracks[2]:group)
+                        1022 group (session.mixers[0].tracks[2]:tracks)
+                        1025 supriya:meters:2 (session.mixers[0].tracks[2]:input-levels)
+                            in_: 22.0, out: 19.0
+                        1023 group (session.mixers[0].tracks[2]:devices)
+                        1024 supriya:channel-strip:2 (session.mixers[0].tracks[2]:channel-strip)
+                            active: c17, bus: 22.0, gain: c18, gate: 1.0
+                        1026 supriya:meters:2 (session.mixers[0].tracks[2]:output-levels)
+                            in_: 22.0, out: 21.0
+                        1027 supriya:patch-cable:2x2 (session.mixers[0].tracks[2].output:synth)
+                            active: c17, gain: 0.0, gate: 1.0, in_: 22.0, out: 16.0
+                1004 supriya:meters:2 (session.mixers[0]:input-levels)
+                    in_: 16.0, out: 1.0
+                1002 group (session.mixers[0]:devices)
+                1003 supriya:channel-strip:2 (session.mixers[0]:channel-strip)
+                    active: 1.0, bus: 16.0, gain: c0, gate: 1.0
+                1005 supriya:meters:2 (session.mixers[0]:output-levels)
+                    in_: 16.0, out: 3.0
+                1013 supriya:patch-cable:2x2 (session.mixers[0].output:synth)
+                    active: 1.0, gain: 0.0, gate: 1.0, in_: 16.0, out: 0.0
+            NODE TREE 1028 group (session.mixers[1]:group)
+                1029 group (session.mixers[1]:tracks)
+                    1034 group (session.mixers[1].tracks[0]:group)
+                        1035 group (session.mixers[1].tracks[0]:tracks)
+                        1038 supriya:meters:2 (session.mixers[1].tracks[0]:input-levels)
+                            in_: 26.0, out: 30.0
+                        1036 group (session.mixers[1].tracks[0]:devices)
+                        1037 supriya:channel-strip:2 (session.mixers[1].tracks[0]:channel-strip)
+                            active: c28, bus: 26.0, gain: c29, gate: 1.0
+                        1039 supriya:meters:2 (session.mixers[1].tracks[0]:output-levels)
+                            in_: 26.0, out: 32.0
+                        1040 supriya:patch-cable:2x2 (session.mixers[1].tracks[0].output:synth)
+                            active: c28, gain: 0.0, gate: 1.0, in_: 26.0, out: 24.0
+                1032 supriya:meters:2 (session.mixers[1]:input-levels)
+                    in_: 24.0, out: 24.0
+                1030 group (session.mixers[1]:devices)
+                1031 supriya:channel-strip:2 (session.mixers[1]:channel-strip)
+                    active: 1.0, bus: 24.0, gain: c23, gate: 1.0
+                1033 supriya:meters:2 (session.mixers[1]:output-levels)
+                    in_: 24.0, out: 26.0
+                1041 supriya:patch-cable:2x2 (session.mixers[1].output:synth)
+                    active: 1.0, gain: 0.0, gate: 1.0, in_: 24.0, out: 0.0
+        """,
+    )
+    assert commands == expected_commands
+
+
+@pytest.mark.xfail
+@pytest.mark.parametrize("online", [False, True])
+@pytest.mark.parametrize("expected_commands, expected_diff", [([], "")])
+@pytest.mark.asyncio
+async def test_Track_set_active(
+    expected_commands: List[Union[OscBundle, OscMessage]],
+    expected_diff: str,
+    mixer: Mixer,
+    online: bool,
+    session: Session,
+    track: Track,
+) -> None:
+    # Pre-conditions
+    if online:
+        await session.boot()
+    # Operation
+    with capture(mixer.context) as commands:
+        await track.set_active()
+    # Post-conditions
+    if not online:
+        raise Exception
+    await assert_diff(
+        session,
+        expected_diff,
+        expected_initial_tree="""
+        """,
+    )
+    assert commands == expected_commands
+    raise Exception
+
+
+@pytest.mark.xfail
+@pytest.mark.parametrize("online", [False, True])
+@pytest.mark.parametrize("expected_commands, expected_diff", [([], "")])
+@pytest.mark.asyncio
+async def test_Track_set_input(
+    expected_commands: List[Union[OscBundle, OscMessage]],
+    expected_diff: str,
+    mixer: Mixer,
+    online: bool,
+    session: Session,
+    track: Track,
+) -> None:
+    # Pre-conditions
+    if online:
+        await session.boot()
+    # Operation
+    with capture(mixer.context) as commands:
+        await track.set_input(None)
+    # Post-conditions
+    if not online:
+        raise Exception
+    await assert_diff(
+        session,
+        expected_diff,
+        expected_initial_tree="""
+        """,
+    )
+    assert commands == expected_commands
+    raise Exception
+
+
+@pytest.mark.parametrize("online", [False, True])
+@pytest.mark.parametrize(
+    "output, maybe_raises, expected_commands, expected_diff",
+    [
+        (
+            "none",
+            does_not_raise,
+            [OscMessage("/n_set", 1025, "gate", 0.0)],
+            """
+            --- initial
+            +++ mutation
+            @@ -23,8 +23,8 @@
+                                         active: c11, bus: 20.0, gain: c12, gate: 1.0
+                                     1017 supriya:meters:2 (session.mixers[0].tracks[0].tracks[0]:output-levels)
+                                         in_: 20.0, out: 15.0
+            -                        1025 supriya:patch-cable:2x2 (session.mixers[0].tracks[0].tracks[0].output:synth)
+            -                            active: c11, gain: 0.0, gate: 1.0, in_: 20.0, out: 18.0
+            +                        1025 supriya:patch-cable:2x2
+            +                            active: c11, gain: 0.0, gate: 0.0, in_: 20.0, out: 18.0
+                             1010 supriya:meters:2 (session.mixers[0].tracks[0]:input-levels)
+                                 in_: 18.0, out: 7.0
+                             1008 group (session.mixers[0].tracks[0]:devices)
+            """,
+        ),
+        (
+            "default",
+            does_not_raise,
+            [],
+            "",
+        ),
+        (
+            "self",
+            pytest.raises(RuntimeError),
+            [],
+            "",
+        ),
+        (
+            "parent",
+            does_not_raise,
+            [],
+            "",
+        ),
+        (
+            "child",
+            does_not_raise,
+            [
+                OscMessage(
+                    "/s_new",
+                    "supriya:fb-patch-cable:2x2",
+                    1049,
+                    0,
+                    1018,
+                    "active",
+                    "c17",
+                    "in_",
+                    30.0,
+                    "out",
+                    22.0,
+                ),
+                OscBundle(
+                    contents=(
+                        OscMessage("/n_set", 1025, "gate", 0.0),
+                        OscMessage(
+                            "/s_new",
+                            "supriya:patch-cable:2x2",
+                            1050,
+                            1,
+                            1012,
+                            "active",
+                            "c11",
+                            "in_",
+                            20.0,
+                            "out",
+                            30.0,
+                        ),
+                    ),
+                ),
+            ],
+            """
+            --- initial
+            +++ mutation
+            @@ -6,6 +6,8 @@
+                                 1012 group (session.mixers[0].tracks[0].tracks[0]:group)
+                                     1013 group (session.mixers[0].tracks[0].tracks[0]:tracks)
+                                         1018 group (session.mixers[0].tracks[0].tracks[0].tracks[0]:group)
+            +                                1049 supriya:fb-patch-cable:2x2 (session.mixers[0].tracks[0].tracks[0].tracks[0].feedback:synth)
+            +                                    active: c17, gain: 0.0, gate: 1.0, in_: 30.0, out: 22.0
+                                             1019 group (session.mixers[0].tracks[0].tracks[0].tracks[0]:tracks)
+                                             1022 supriya:meters:2 (session.mixers[0].tracks[0].tracks[0].tracks[0]:input-levels)
+                                                 in_: 22.0, out: 19.0
+            @@ -23,8 +25,10 @@
+                                         active: c11, bus: 20.0, gain: c12, gate: 1.0
+                                     1017 supriya:meters:2 (session.mixers[0].tracks[0].tracks[0]:output-levels)
+                                         in_: 20.0, out: 15.0
+            -                        1025 supriya:patch-cable:2x2 (session.mixers[0].tracks[0].tracks[0].output:synth)
+            -                            active: c11, gain: 0.0, gate: 1.0, in_: 20.0, out: 18.0
+            +                        1025 supriya:patch-cable:2x2
+            +                            active: c11, gain: 0.0, gate: 0.0, in_: 20.0, out: 18.0
+            +                        1050 supriya:patch-cable:2x2 (session.mixers[0].tracks[0].tracks[0].output:synth)
+            +                            active: c11, gain: 0.0, gate: 1.0, in_: 20.0, out: 30.0
+                             1010 supriya:meters:2 (session.mixers[0].tracks[0]:input-levels)
+                                 in_: 18.0, out: 7.0
+                             1008 group (session.mixers[0].tracks[0]:devices)
+            """,
+        ),
+        (
+            "mixer",
+            does_not_raise,
+            [
+                OscBundle(
+                    contents=(
+                        OscMessage("/n_set", 1025, "gate", 0.0),
+                        OscMessage(
+                            "/s_new",
+                            "supriya:patch-cable:2x2",
+                            1049,
+                            1,
+                            1012,
+                            "active",
+                            "c11",
+                            "in_",
+                            20.0,
+                            "out",
+                            16.0,
+                        ),
+                    ),
+                ),
+            ],
+            """
+            --- initial
+            +++ mutation
+            @@ -23,8 +23,10 @@
+                                         active: c11, bus: 20.0, gain: c12, gate: 1.0
+                                     1017 supriya:meters:2 (session.mixers[0].tracks[0].tracks[0]:output-levels)
+                                         in_: 20.0, out: 15.0
+            -                        1025 supriya:patch-cable:2x2 (session.mixers[0].tracks[0].tracks[0].output:synth)
+            -                            active: c11, gain: 0.0, gate: 1.0, in_: 20.0, out: 18.0
+            +                        1025 supriya:patch-cable:2x2
+            +                            active: c11, gain: 0.0, gate: 0.0, in_: 20.0, out: 18.0
+            +                        1049 supriya:patch-cable:2x2 (session.mixers[0].tracks[0].tracks[0].output:synth)
+            +                            active: c11, gain: 0.0, gate: 1.0, in_: 20.0, out: 16.0
+                             1010 supriya:meters:2 (session.mixers[0].tracks[0]:input-levels)
+                                 in_: 18.0, out: 7.0
+                             1008 group (session.mixers[0].tracks[0]:devices)
+            """,
+        ),
+        (
+            "sibling",
+            does_not_raise,
+            [
+                OscBundle(
+                    contents=(
+                        OscMessage("/n_set", 1025, "gate", 0.0),
+                        OscMessage(
+                            "/s_new",
+                            "supriya:patch-cable:2x2",
+                            1049,
+                            1,
+                            1012,
+                            "active",
+                            "c11",
+                            "in_",
+                            20.0,
+                            "out",
+                            24.0,
+                        ),
+                    ),
+                ),
+            ],
+            """
+            --- initial
+            +++ mutation
+            @@ -23,8 +23,10 @@
+                                         active: c11, bus: 20.0, gain: c12, gate: 1.0
+                                     1017 supriya:meters:2 (session.mixers[0].tracks[0].tracks[0]:output-levels)
+                                         in_: 20.0, out: 15.0
+            -                        1025 supriya:patch-cable:2x2 (session.mixers[0].tracks[0].tracks[0].output:synth)
+            -                            active: c11, gain: 0.0, gate: 1.0, in_: 20.0, out: 18.0
+            +                        1025 supriya:patch-cable:2x2
+            +                            active: c11, gain: 0.0, gate: 0.0, in_: 20.0, out: 18.0
+            +                        1049 supriya:patch-cable:2x2 (session.mixers[0].tracks[0].tracks[0].output:synth)
+            +                            active: c11, gain: 0.0, gate: 1.0, in_: 20.0, out: 24.0
+                             1010 supriya:meters:2 (session.mixers[0].tracks[0]:input-levels)
+                                 in_: 18.0, out: 7.0
+                             1008 group (session.mixers[0].tracks[0]:devices)
+            """,
+        ),
+        (
+            "other_mixer",
+            pytest.raises(RuntimeError),
+            [],
+            "",
+        ),
+    ],
+)
+@pytest.mark.asyncio
+async def test_Track_set_output(
+    expected_commands: List[Union[OscBundle, OscMessage]],
+    expected_diff: str,
+    maybe_raises,
+    mixer: Mixer,
+    online: bool,
+    output: str,
+    session: Session,
+    track: Track,
+) -> None:
+    # Pre-conditions
+    subtrack = await track.add_track()
+    subsubtrack = await subtrack.add_track()
+    sibling = await mixer.add_track()
+    targets: Dict[str, Optional[Union[Default, TrackContainer]]] = {
+        "child": subsubtrack,
+        "default": DEFAULT,
+        "mixer": mixer,
+        "none": None,
+        "other_mixer": await session.add_mixer(),
+        "parent": track,
+        "self": subtrack,
+        "sibling": sibling,
+    }
+    if online:
+        await session.boot()
+        await debug_tree(session)
+    # Operation
+    with maybe_raises, capture(mixer.context) as commands:
+        await subtrack.set_output(targets[output])
+    # Post-conditions
+    if not online:
+        return
+    await assert_diff(
+        session,
+        expected_diff,
+        expected_initial_tree="""
+        <session.contexts[0]>
+            NODE TREE 1000 group (session.mixers[0]:group)
+                1001 group (session.mixers[0]:tracks)
+                    1006 group (session.mixers[0].tracks[0]:group)
+                        1007 group (session.mixers[0].tracks[0]:tracks)
+                            1012 group (session.mixers[0].tracks[0].tracks[0]:group)
+                                1013 group (session.mixers[0].tracks[0].tracks[0]:tracks)
+                                    1018 group (session.mixers[0].tracks[0].tracks[0].tracks[0]:group)
+                                        1019 group (session.mixers[0].tracks[0].tracks[0].tracks[0]:tracks)
+                                        1022 supriya:meters:2 (session.mixers[0].tracks[0].tracks[0].tracks[0]:input-levels)
+                                            in_: 22.0, out: 19.0
+                                        1020 group (session.mixers[0].tracks[0].tracks[0].tracks[0]:devices)
+                                        1021 supriya:channel-strip:2 (session.mixers[0].tracks[0].tracks[0].tracks[0]:channel-strip)
+                                            active: c17, bus: 22.0, gain: c18, gate: 1.0
+                                        1023 supriya:meters:2 (session.mixers[0].tracks[0].tracks[0].tracks[0]:output-levels)
+                                            in_: 22.0, out: 21.0
+                                        1024 supriya:patch-cable:2x2 (session.mixers[0].tracks[0].tracks[0].tracks[0].output:synth)
+                                            active: c17, gain: 0.0, gate: 1.0, in_: 22.0, out: 20.0
+                                1016 supriya:meters:2 (session.mixers[0].tracks[0].tracks[0]:input-levels)
+                                    in_: 20.0, out: 13.0
+                                1014 group (session.mixers[0].tracks[0].tracks[0]:devices)
+                                1015 supriya:channel-strip:2 (session.mixers[0].tracks[0].tracks[0]:channel-strip)
+                                    active: c11, bus: 20.0, gain: c12, gate: 1.0
+                                1017 supriya:meters:2 (session.mixers[0].tracks[0].tracks[0]:output-levels)
+                                    in_: 20.0, out: 15.0
+                                1025 supriya:patch-cable:2x2 (session.mixers[0].tracks[0].tracks[0].output:synth)
+                                    active: c11, gain: 0.0, gate: 1.0, in_: 20.0, out: 18.0
+                        1010 supriya:meters:2 (session.mixers[0].tracks[0]:input-levels)
+                            in_: 18.0, out: 7.0
+                        1008 group (session.mixers[0].tracks[0]:devices)
+                        1009 supriya:channel-strip:2 (session.mixers[0].tracks[0]:channel-strip)
+                            active: c5, bus: 18.0, gain: c6, gate: 1.0
+                        1011 supriya:meters:2 (session.mixers[0].tracks[0]:output-levels)
+                            in_: 18.0, out: 9.0
+                        1026 supriya:patch-cable:2x2 (session.mixers[0].tracks[0].output:synth)
+                            active: c5, gain: 0.0, gate: 1.0, in_: 18.0, out: 16.0
+                    1027 group (session.mixers[0].tracks[1]:group)
+                        1028 group (session.mixers[0].tracks[1]:tracks)
+                        1031 supriya:meters:2 (session.mixers[0].tracks[1]:input-levels)
+                            in_: 24.0, out: 25.0
+                        1029 group (session.mixers[0].tracks[1]:devices)
+                        1030 supriya:channel-strip:2 (session.mixers[0].tracks[1]:channel-strip)
+                            active: c23, bus: 24.0, gain: c24, gate: 1.0
+                        1032 supriya:meters:2 (session.mixers[0].tracks[1]:output-levels)
+                            in_: 24.0, out: 27.0
+                        1033 supriya:patch-cable:2x2 (session.mixers[0].tracks[1].output:synth)
+                            active: c23, gain: 0.0, gate: 1.0, in_: 24.0, out: 16.0
+                1004 supriya:meters:2 (session.mixers[0]:input-levels)
+                    in_: 16.0, out: 1.0
+                1002 group (session.mixers[0]:devices)
+                1003 supriya:channel-strip:2 (session.mixers[0]:channel-strip)
+                    active: 1.0, bus: 16.0, gain: c0, gate: 1.0
+                1005 supriya:meters:2 (session.mixers[0]:output-levels)
+                    in_: 16.0, out: 3.0
+                1034 supriya:patch-cable:2x2 (session.mixers[0].output:synth)
+                    active: 1.0, gain: 0.0, gate: 1.0, in_: 16.0, out: 0.0
+            NODE TREE 1035 group (session.mixers[1]:group)
+                1036 group (session.mixers[1]:tracks)
+                    1041 group (session.mixers[1].tracks[0]:group)
+                        1042 group (session.mixers[1].tracks[0]:tracks)
+                        1045 supriya:meters:2 (session.mixers[1].tracks[0]:input-levels)
+                            in_: 28.0, out: 36.0
+                        1043 group (session.mixers[1].tracks[0]:devices)
+                        1044 supriya:channel-strip:2 (session.mixers[1].tracks[0]:channel-strip)
+                            active: c34, bus: 28.0, gain: c35, gate: 1.0
+                        1046 supriya:meters:2 (session.mixers[1].tracks[0]:output-levels)
+                            in_: 28.0, out: 38.0
+                        1047 supriya:patch-cable:2x2 (session.mixers[1].tracks[0].output:synth)
+                            active: c34, gain: 0.0, gate: 1.0, in_: 28.0, out: 26.0
+                1039 supriya:meters:2 (session.mixers[1]:input-levels)
+                    in_: 26.0, out: 30.0
+                1037 group (session.mixers[1]:devices)
+                1038 supriya:channel-strip:2 (session.mixers[1]:channel-strip)
+                    active: 1.0, bus: 26.0, gain: c29, gate: 1.0
+                1040 supriya:meters:2 (session.mixers[1]:output-levels)
+                    in_: 26.0, out: 32.0
+                1048 supriya:patch-cable:2x2 (session.mixers[1].output:synth)
+                    active: 1.0, gain: 0.0, gate: 1.0, in_: 26.0, out: 0.0
+        """,
+    )
+    assert commands == expected_commands
+
+
+@pytest.mark.xfail
+@pytest.mark.parametrize("online", [False, True])
+@pytest.mark.parametrize(
+    "expected_commands, expected_diff",
+    [
+        ([], ""),
+    ],
+)
+@pytest.mark.asyncio
+async def test_Track_set_soloed(
+    expected_commands: List[Union[OscBundle, OscMessage]],
+    expected_diff: str,
+    mixer: Mixer,
+    online: bool,
+    session: Session,
+    track: Track,
+) -> None:
+    # Pre-conditions
+    if online:
+        await session.boot()
+    # Operation
+    with capture(mixer.context) as commands:
+        await track.set_soloed()
+    # Post-conditions
+    if not online:
+        raise Exception
+    await assert_diff(
+        session,
+        expected_diff,
+        expected_initial_tree="""
+        """,
+    )
+    assert commands == expected_commands
+    raise Exception
+
+
+@pytest.mark.xfail
+@pytest.mark.parametrize("online", [False, True])
+@pytest.mark.parametrize(
+    "expected_commands, expected_diff",
+    [
+        ([], ""),
+    ],
+)
+@pytest.mark.asyncio
+async def test_Track_ungroup(
+    expected_commands: List[Union[OscBundle, OscMessage]],
+    expected_diff: str,
+    mixer: Mixer,
+    online: bool,
+    session: Session,
+    track: Track,
+) -> None:
+    # Pre-conditions
+    if online:
+        await session.boot()
+    # Operation
+    with capture(mixer.context) as commands:
+        await track.ungroup()
+    # Post-conditions
+    if not online:
+        raise Exception
+    await assert_diff(
+        session,
+        expected_diff,
+        expected_initial_tree="""
+        """,
+    )
+    assert commands == expected_commands
+    raise Exception