Of course music doesn't exist independently of humanity - music grows out of existing culture and also forms the raw material for evolution of new cultures.
You're correct in saying that it is one of the forms that resonate among people of a certain group, and acts as part of the 'glue', so to speak, that holds together a group that has those particular customs and traditions in common. Where I think you're wrong though, is to suggest this only as a negative thing, as only having an exclusive use as if to separate one group from another.
While it's true that music has a military or patriotic use, it has others as well - music is created to accompany the expression of feelings about a whole spectrum of experience, of romantic love, maternal love, the beauty of nature, the pain and anguish of loss, and one could go on. In fact, because of this, I think that music and all the arts for that matter have a more unifying than separating role among peoples because music can reach across the boundaries between groups in ways that other forms of communication may not. People can understand each others' arts even while they may not understand each others' language, because the arts can allow us access something fundamental and common to all human experience, not just the experience of your own group. Cultural exchange can build bridges because it allows one people to come to know another people's spirit, it can give us a whole new window into other peoples' experiences, even across distance and time. It's just so much more than just all 'whole tribes unanimously giving out the same call'.