I don’t remember where I got this link — probably MeFi — but Metamix is way way cool.
It takes an mp3 or other soundfile and makes a strange, mathematically based extended remix of it. You can play with the parameters to give different effects.
Oh, and I do mean “extended.” This is for playing in the background. Over long periods of time. Metamixed songs are potentially infinite, and they progress very slowly back and forth through the original piece.
I’m listening to a Metamixed version of Matt Hyland by Cooper, Nelson & Early right now and it’s oddly repetitive but beautiful.
Some songs work better than others with it. Hard to predict.