I recall discussing somewhere here about generative soundtracks and use in video games in the VW thread, and at the time potential in use in a racing game.
Check this out:
http://www.vice.com/read/no-mans-sky...ource=vicefbus
Every bit of the in-game soundtrack is generated using the different iterations of melodies and sounds created by a band to make an album. The music changes and grows based on what you do with your character in game, as well as adjusts based on environment, which is all also procedurally generated.