Ambience slider = music in most custom maps.  I don't make maps, I don't understand why, it just is.
[URL=https://addons.mozilla.org/firefox/1174]<img src="http://img146.imageshack.us/img146/9098/20080819022938qp5.jpg" width="800" height="600">[/URL]
If you want the rest of my sound settings, here's my computer's sound setting:
[img:8ef922cd1c]http://img503.imageshack.us/img503/4863/20080819023243xe7.jpg[/img:8ef922cd1c]
I have a pair of cheap desktop speakers turned up to about 90% of max volume.