I mostly play games without music in the background these days. I prefer to get more 'immersed' in the game environment, so I prefer more 'ambient sounds' to music.
However, JK is one of the games I'll make an exception. I keep the music low in the background.
I'm not sure what your problem is BawBag, because I've not had a problem turning the music down. I use Win98SE and an SB Live soundcard. Maybe you need to update your sound drivers or something.
Anyway, good luck with your problem.