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?