information:extraction, structural:scholar_edition
Valves

Valves are used to change the length of tubing of a brass instrument allowing the player to reach the notes of various harmonic series. Each valve pressed diverts the air stream through additional tubing, individually or in conjunction with other valves. This lengthens the vibrating air column thus lowering the fundamental tone and associated harmonic series produced by the instrument. Designs exist, although rare, in which this behaviour is reversed, i.e., pressing a valve removes a length of tubing rather than adding one. One modern example of such an ascending valve is the Yamaha YSL-350C trombone, in which the extra valve tubing is normally engaged to pitch the instrument in B ♭, and pressing the thumb lever removes a whole step to pitch the instrument in C. Valves require regular lubrication.

A core standard valve layout based on the action of three valves had become almost universal by (at latest) 1864 as witnessed by Arban's method published in that year. The effect of a particular combination of valves may be seen in the table below. This table is correct for the core three-valve layout on almost any modern valved brass instrument. The most common four-valve layout is a superset of the well-established three-valve layout and is noted in the table, despite the exposition of four-valve and also five-valve systems (the latter used on the tuba) being incomplete in this article.