slide

It has an extendable slide that can increase the length of the instrument’s tubing. The slide thus performs the function of the valves on other brass instruments. From the 19th century, some trombones have been made with valves, but their use was never universal.

The U-shaped slide moves along the two stationary tubes, lowering the fundamental by a half step with each lower slide position and making available the notes of seven harmonic series.