ET Trumpet Mutes (also known as wah wah) are a hollow, bulbous mute in two parts. Unlike the more common straight or cup mutes, the Harmon mute has a solid ring of cork that completely blocks the air leaving the bell, forcing all of it into the mute. At the front of ET Trumpet Mutes, there is a cup on a tube (sometimes called the “stem”) that can be slid in or out, or removed completely, depending on the composer’s direction or the player’s preference. This mute produces a tinny, shallow sound which can be varied by adjusting the mute and via manipulation with the fingers at the cup end. Harmon mutes are commonly used only on trumpets and trombones.

Miles Davis often played through a Harmon mute without the stem. This formed a characteristic sound, and greatly influenced the jazz community in such classic tracks as “All Blues“.