I don't think it's sufficient to say we enjoy music because we evolved to hear animal noises. This lazy hand-waving explanation can hardly be called a hypothesis. Hitting something with a stick and making sounds with your voice is something a cave man could do. We're talking about something so old that it likely evolved and developed with us as a species. Birdsong developed through sexual selection. That's not too far from what we see in our species, to be honest.