Jam Track Audio Streams Encrypted

[Alex1331xela]

Hi, I'm noticing that for Jam Tracks (Sparks tracks)'s audio, preview audios (pid) are not encrypted, but for the other types (sid, stereoId, instrumentalId) the audio streams seem to be encrypted with ClearKey behind a "key.key" (as seen in the track's b64 encrpted xml). I was just wondering if you'd have any knowledge/documentation on this? Thanks so much!