Custom music addon from CE

ill definitely try this, I was also trying to find out how achievement system works in cqm the other day and i managed to reverse a few files but i still can't trace the main script that fires up the thing yet. Maybe some entity in the maps trigger it too, I'm still new to modding source games so im sorry if I said something dumb lol, I've never tried to mod anything this old before, its a wild ride indeed