Why Does a Trumpet Have Valves?
Valves in a trumpet enable the player to lower, momentarily, the pitch of the note he wishes to make. What happens when one of the valves is pushed down is that the air is diverted through a small loop of tube thus lowering the pitch or sound of the instrument. When the first valve is pressed, usually by the first finger, the pitch of the trumpet will be lowered by a whole tone. The second valve, according to the same principle, lowers the sound by a semitone, and the third lowers it by a minor third.
Nearly all trumpets and brass instruments today are made with valves. The mechanism was invented in 1815 by two Germans. Today most valves are of the piston type with springs to return the valves to their original position. The history of trumpets dates back to 1500 BC in Egypt. But until the beginning of the 19th Century all the variations produced by valves had to be made by the player controlling his breath.
Brass instrument 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. Valves in brass instruments require regular maintenance and lubrication to ensure fast and reliable movement.
Modern trumpets have three (or, infrequently, four) piston valves, each of which increases the length of tubing when engaged, thereby lowering the pitch. The first valve lowers the instrument’s pitch by a whole step (two semitones), the second valve by a half step (one semitone), and the third valve by one and a half steps (three semitones). When a fourth valve is present (as with some piccolo trumpets), it usually lowers the pitch a perfect fourth (five semitones). Used singly and in combination these valves make the instrument fully chromatic, i.e., able to play all twelve pitches of classical music.
The pitch of the trumpet can be raised or lowered by the use of the tuning slide. Pulling the slide out lowers the pitch; pushing the slide in raises it. To overcome the problems of intonation and reduce the use of the slide, Renold Schilke designed the tuning-bell trumpet. Removing the usual brace between the bell and a valve body allows the use of a sliding bell; the player may then tune the horn with the bell while leaving the slide pushed in, or nearly so, thereby improving intonation and overall response.
A trumpet becomes a closed tube when the player presses it to the lips; therefore, the instrument only naturally produces every other overtone of the harmonic series. The shape of the bell makes the missing overtones audible. Most notes in the series are slightly out of tune and modern trumpets have slide mechanisms for the first and third valves with which the player can compensate by throwing (extending) or retracting one or both slides, using the left thumb and ring finger for the first and third valve slides respectively.