Darwin tunes is an experiment designed to test the evolution of music. Small 15 sec loops are played and rated by volunteers, and those that do well reproduce. So what do we get when reproduction and selection? EVOLUTION!
The official experiment is over now, but you can still rate and listen as well as listen to archived medleys to see how the music has changed over time. Also, you are free to download and use these clips non-commercially. Some of the loops would be rather stunning used as background music for educational youtube vids and the like.
DarwinTunes medley at 500 generations by uncoolbob