Have you seen the 'infinite jukebox'?

http://labs.echonest.com/Uploader/index.html

It stretches or compresses existing music by jumping back and forth to parts of the piece that sound similar, which could be handy for dynamically adapting the timing/duration of existing pieces to the players situation.

That is an awesome idea. I can imagine it would be cool in your standard one-on-one fighting games where the music could get more intense when then battle becomes more intense.