At first glance the answer is obvious. Music is not essential to the two main functions of being alive, that of metabolism and reproduction. But wait, back to our original question. If we could answer this, then maybe it would go a long way in answering the second question. Another interesting point.
Music is old.
It's been around forever, as far as we know. Both are symbolic. And if we look at children, babies, we see that even before language develops there is and inborn sense of rhythm. Babies bounce to music, they dance, sway and bob. Their little eyes beam with delight at the simplest of tunes, long before they can speak.