When adding stuff into a game it's a very wise thing to look at the debug file, it's not that hard to figure out.
the file is called debug.log, after that, I'd search for the name of the song that you put in the xml file of the map.
So, check debug.log for your song name and check what's wrong with it, propably just a directory mistake, or that you added .ogg to the name you entered in the xml file, I don't know, I personally can't help you much further without more information.