A mute is a device which alters the timbre and/or reduces the volume of a musical instrument.
Mouthpiece Express sell mutes by several leading manufactures -- straight mutes, cup mutes, "Harmon" mutes, stop mutes... Click your instrument to browse.
Yamaha Silent Brass
We also have Yamaha Silent Brass products including: mutes, personal studio modules, complete systems, pickup mics, and Silent Brass carrying cases. Click Yamaha Silent Brass.
And don't forget the Mute Bag!