The trombone is a musical instrument in the brass family. Like all brass instruments, sound is produced when the player’s vibrating lips (embouchure) cause the air column inside the instrument to vibrate. Nearly all trombones have a telescoping slide mechanism that varies the length of the instrument to change the pitch. Instead of a slide, the valve trombone has three valves like those on a trumpet.
The word trombone derives from Italian tromba (trumpet) and -one (a suffix meaning "large"), so the name means "large trumpet". The trombone has a predominantly cylindrical bore like its valved counterpart the baritone horn and in contrast to its conical valved counterparts, the euphonium and the orchestral horn. The most frequently encountered trombones are the tenor trombone and bass trombone. The E♭ alto trombone became less common as tenor technique extended the upper range of that instrument, but is now enjoying a resurgence as the importance of its lighter sonority in many classical and early romantic works is appreciated. The most common variant, the tenor, is pitched in B♭, an octave below the B♭ trumpet and an octave above the B♭ tuba. Trombone music, along with music for euphonium and tuba, is typically written in concert pitch, although exceptions do occur, notably in almost all brass band music where tenor trombone is presented as a B♭ transposing instrument.
A brass instrument is a musical instrument that produces sound by sympathetic vibration of air in a tubular resonator in sympathy with the vibration of the player's lips. Brass instruments are also called labrosones, literally meaning "lip-vibrated instruments".
There are several factors involved in producing different pitches on a brass instrument. Slides, valves, crooks, or keys are used to change vibratory length of tubing, thus changing the available harmonic series, while the player's embouchure, lip tension and air flow serve to select the specific harmonic produced from the available series.
The view of most scholars (see organology) is that the term "brass instrument" should be defined by the way the sound is made, as above, and not by whether the instrument is actually made of brass. Thus one finds brass instruments made of wood, like the alphorn, the cornett, the serpent and the didgeridoo, while some woodwind instruments are made of brass, like the saxophone.