When you add music to your map you need to put the .mp3 files into your music folder.
You're then going to go into your music.cfg and instead of where it says /sounds you'd type /music.
When you put it in your sounds folder, the only way you'll hear the music in your map is if your Effects volume is turned up, while if it's in your music folder, you'll hear it with your Music volume turned up.
Make sure you turn the Effects volume up in your options if you plan on keeping the music files in your sounds folder.