Well, as I have allready implented this in my source I have some suggestions for you; make skillbooks that play music. Just use an un-used skill and change the sound of it to some sort of song. It's a good trick.
Adding music to certain maps would be a little more complicated, and I doubt you would be able to do it. So I would reccomend the skillbooks.
Edit: Just remembered, there are items called MusicBook too, use that. Just add a code for it which opens a file in the persons client. (it would of course require a patch.)