Adding your own music to a map is ez.
1. Convert your music to .wav form.
2. Import it to your map via the editor.
3. Set up a trigger to play it in a loop
ie... Always
Play wav file
Wait ???? milliseconds (at least as long as the music plays)
Preserve trigger
Then deactivate the game music sound track while playing the game.
Drawbacks......
1. It only works in an UMS game.
2. Your map will be about 3 meg in size.
Unless it is a 1 person game, or you and your teamates
have DSL or better, nobody will want to sit through the
1 hour download.