trombone [Ital.,=large trumpet], brass wind musical instrument of cylindrical bore, twice bent on itself, having a sliding section that lengthens or shortens it and thus regulates the pitch. The descendant of the sackbut, it was developed in the 15th cent. by adding a slide to the trumpet. Early representations of the instrument show it nearly in its present form. Despite its continuous possession of a complete chromatic scale, which was lacking in early trumpets and the French horn, the trombone was far behind them in acceptance into the orchestra. In the 16th cent. it became popular for court and church music. In the 18th cent. it entered the opera orchestra, and Beethoven introduced it into symphonic music. In the enlarged orchestra of the 19th cent., the trombone became increasingly important, being valued for its wide range in pitch and dynamics. It is more often used as an ensemble than as a solo instrument in the orchestra, and it has little solo literature. Three trombones are standard in the orchestra, formerly alto, tenor, and bass. The tenor is most often used today, often with extra tubing that can be cut in by a valve to give it the lower notes of the old bass trombone. The trombone is also widely used in jazz and dance bands. A valved trombone, first produced in Vienna in the 1820s, is frequently used in Latin countries, and by some jazz musicians, but is inferior in tone quality to the slide trombone.

Brass instrument with an extendable slide with which the length of its tubing can be increased. It has a mostly cylindrical bore and a cup-shaped mouthpiece. The slide performs the same function as the valves in other brass instruments. Valve trombones, both with and without slides, were developed in the early 19th century; they provide increased agility but diminished tone quality. The trombone exists in several sizes; the tenor trombone in B-flat is the standard instrument, but the bass trombone is also used orchestrally. The trombone (long known as the sackbut) developed in the 15th century and has changed little over 400 years. By the 16th century it had been adopted by town, court, church, and military bands; it was employed in early opera orchestras, but it only began to be used in the symphony orchestra circa 1800. In the 20th century it became important in dance and jazz bands.

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