Today I have identified 10 Suggestions related to Sounds on Roll20, and created an Index of them.
Malcom, your suggestion might gain some power by adding your Comment and Vote on the existing Suggestion thread called "Alternatives to Soundcloud", because your idea is closely related, and we can gain some traction for this by voting together and listing your Private Playlists ideas there too:
"Alternatives to Soundcloud" suggestion,
https://app.roll20.net/forum/post/1245252/alternat...Please check out the link and crosspost your comment from above, on there, if you like. Note that your suggestion thread is equally valid on its own, but I thought that you might want to consider combining.