I always envisioned an audio stream in which you can't skip songs, but you may mute the song if you don't like it until a new one comes on. Songs were streamed from a specific folder, and if the user preferred, he could automatically have this folder updated by connecting to a central server, which provided additional 64kbps MP3 (or non-proprietary alternative) sporadically. This would allow users to add their own songs, but also give the music a "radio" feel by streaming audio and coming out with new songs every once in a while. Then if the game developer decided to stop releasing music/updates the game would continue to run without any alterations, or perhaps even allow the game support to be picked up by a third-party by altering the server address.
I've always felt all PC games (and nowadays console games since everybody's online) should have this system for in-game music. By including a "remove file" script into your update you could easily add and remove songs, or even commercials, from the listeners audio stream.
The music options might appear as:
Enable Music: boolean
Volume: byte
Play in Order/Shuffle: boolean
Enable Music Updates: boolean
Music Server: xx.xx.xx.xx
Download Commercials: boolean
Don't Remove Old Music/Commercials: boolean

