Some brass instruments like trumpets and trombones often usemutes to change the sound of their instrument during some songs(often happens in jazz, normally written into the music). You canbuy them, but I know that trombones can actually use toiletplungers (clean of course) as mutes in a pinch. They create a lessdeep and whole tone, its almost like they take the buzz out of thenoise, it's really cool sounding.