I tend to side with ladylazurus on this one. Indeed simple music may well have had a sexual aspect. But my understanding is that original drums were used for distant communication, like a forerunner to morse code.
I think man learned that he could IMPART what he was FEELING via music, a feat that words are not suited especially well for. And yes, Music = Mathmatics, 100% Listen to Bach. Hehe. As for the groupies... I find it hard to accept that Mozart wrote his majestic pieces to "wow the babes".
Music has a peculiar way of expressing so much that would sound hollow if rendered into words. I think it is more likely as to have simply originated as an alternate form of communication, than as rutting accompaniment or prelude.