I have generated quite a bit of music using evolutionary algorithms. My research is mostly about figuring out representations that are not at too low a level (eg 1 "gene" per note). I like representations that in some way represent the patterns, oscillations, and processes that seem to drive music forward over time.

A paper: http://ncra.ucd.ie/papers/gecco2011_jmcdermott.pdf

Some short mp3s: http://www.skynet.ie/~jmmcd/software/GraphMusicDemoPieces.tg...

Longer, slow-developing stuff on soundcloud (using slightly different software): http://soundcloud.com/jmmcd/tomorrow-is-a-new-day