I couldn't help but notice that most responses are concentrating on individual benefits, even though one did mention that individuals don't evolve, but rather populations do.
Consider this the next time you're sitting around a campfire having a sing-a-long:
We are social animals, which is arguably the greatest survival trait that we have acquired. Other traits we may develop that promote or support social cohesion should be selected for and those that endanger social cohesion should be selected against.
Music, singing, and dancing are social activities that promote social cohesion and a sense of being a part of the group. The same goes for engaging in any kind of ritual, which becomes apparent in religious and military rituals.
I would suspect that music appreciation, including sexual selection based thereupon, developed later. Again, just observing most group sing-a-longs should show that music appreciation very rarely comes into play there, rather it's the group activity and the resultant cameraderie.
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