Music is important to us. Why?

It seems that humans cannot exist without producing music (or at least without enjoying it).  What is it about our nature that makes us so responsive to music?  It comforts us when we're upset, it raises our spirits, gets our blood pumping, makes us horny, etc..
Are humans prewired to find beauty in the mathematical harmonies and rythems?  What is it about music that makes it nearly impossible to live without?

>>1
Once we developed sentience, we began to be really aware of everything around us.  Presumably, we started hitting things out of boredome and started, with our amazing awareness, to realize that some of it sounded pretty cool.  So we reproduced these sounds (refer to Mel Brooks's History of the World) and the art of noise was along the way melded into storytelling, and thus ballads were born.

Once solid governments and capitalistic ideals were in place, we  found ourselves with a lot of time on our hands.  Because of the wonderful hierarchy, those who were not slaving on the fields had an almost depressing amount of time to spare.  And so they elaborated on the arts; writing, drawing, and music.  Listening to music became a passtime in itself.