thumb|A street brass quartet
In music, a quartet (, , , , ) is an ensemble of four singers or instrumental performers.
Classical
String quartet
right|thumb|A string quartet in performance. From left to right - violin 1, violin 2, cello, viola
In classical music, one of the most common combinations of four instruments in chamber music is the string quartet. String quartets most often consist of two violins, a viola, and a cello. The particular choice and number of instruments derives from the registers of the human voice: soprano, alto, tenor and bass (SATB). In the string quartet, two violins play the soprano and alto vocal registers, the viola plays the tenor register and the cello plays the bass register.
Composers of notable string quartets include Joseph Haydn (68 compositions), Wolfgang Amadeus Mozart (23), Ludwig van Beethoven (16), Franz Schubert (15), Felix Mendelssohn (6), Johannes Brahms (3), Antonín Dvořák (14), Alexander Borodin (2), Béla Bartók (6), Elizabeth Maconchy (13), Darius Milhaud (18), Heitor Villa-Lobos (17), and Dmitri Shostakovich (15).