Good article at http://en.wikipedia.org/wiki/Music_therapy

which hot links to aspects of music and our human responses: clinical therapy, biomusicology, musical acoustics, music theory, psychoacoustics, embodied music cognition, aesthetics of music, and comparative musicology.

I'd also point out that I've had birds come around to either tell me shush or to find out what was going on with the guitar. So I think music affects the animal kingdom too. Cows and milk and classical music for example. I'm of the opinion that wars should be fought by musicians, because it's real hard to kill someone who shares your groove. It would involve but one death: that of the first person to suggest that only his/her music should be played. That oughta settle down the rest.