(Fr. piston; Ger. Ventil; It. pistone).
Mechanism invented c.1813 by the horn‐player Heinrich Stölzel and improved in 1818 in collaboration with Friedrich Blühmel, whereby all the notes of the chromatic scale were made available to brass instr. Pitch altered by increasing or decreasing length of tube through which wind must go to produce sound (except normal trombones, for which slide is sufficient). 2 types in use, piston, in which piston works up and down in casing, and rotary, a 4‐way stop‐cock turning in cylindrical case and governed by a spring. Credit for the first type of valve must go to Charles Clagget, an Irishman, who patented an invention in 1788 which enabled pitch to be altered by means of a lever.