The term string quartet can refer to either a type of musical composition or a group of four people who play them. Many composers from the mid-18th century onwards wrote string quartets. The associated musical ensemble consists of two violinists, a violist, and a cellist.

The Emerson String Quartet, also known as the Emerson Quartet, was an American string quartet initially formed as a student group at the Juilliard School in 1976. It was named for American poet and philosopher Ralph Waldo Emerson and began touring professionally in 1976. The ensemble taught in residence at The Hartt School in the 1980s and is currently the quartet in residence at Stony Brook University. Both of the founding violinists studied with Oscar Shumsky at Juilliard, and the two alternated as first and second violinists for the group. The Emerson Quartet was one of the first such ensembles with the two violinists alternating chairs.

The Fine Arts Quartet is a chamber music ensemble founded in Chicago, United States in 1946 by Leonard Sorkin and George Sopkin. The Quartet has recorded over 200 works and has toured internationally for 77 years, making it one of the longest enduring major string quartets. In its history, the Quartet has had two leaders: Leonard Sorkin, from 1946 to 1981, and Ralph Evans, from 1982 to the present. Its current members are violinists Ralph Evans and Efim Boico, violist Gil Sharon, and cellist Niklas Schmidt.

The Pavel Haas Quartet is a Czech string quartet which was founded in 2002. Their first album with the second quartets of Haas and Janáček won the 2007 Gramophone Award for Chamber music. The Gramophone reviewer David Fanning described their playing as "streamlined but full-blooded". Their recording of the Dvořák String Quartets Op. 106 & 96 won the Gramophone Awards' most coveted "Recording of the Year" prize in 2011.

The Quartetto Italiano was a string quartet founded in Reggio Emilia in 1945. They made their debut in 1945 in Carpi when all four players were still in their early 20s. They were originally named Nuovo Quartetto Italiano before dropping the "Nuovo" tag in 1951. They are particularly noted for their recording of the complete cycle of Beethoven string quartets, made between 1967 and 1975. The quartet disbanded in 1980.

Rudolf Borisovich Barshai was a Soviet and Russian conductor and violist.

String Quartet No. 3 is the third of seventeen works in the medium by the Brazilian composer Heitor Villa-Lobos, and was written in 1916. A performance lasts approximately twenty-three minutes.

String Quartet No. 5 is the fifth of seventeen works in the genre by the Brazilian composer Heitor Villa-Lobos, written in 1931. A performance lasts approximately 17 minutes.

String Quartet No. 6 ("Brazilian") is one of seventeen works in the genre by the Brazilian composer Heitor Villa-Lobos, and was written in 1938, in between his early and late periods. Villa-Lobos considered naming it "Quartet Popular No. 2" as opposed to "Brazilian," and while the work is indeed one of his more nationalist pieces, it also bears direct connections to the Viennese tradition of string quartet composition. A performance lasts approximately 24 minutes.

String Quartet No. 12 is the part of a series of seventeen works in the genre by the Brazilian composer Heitor Villa-Lobos, and was written in 1950. A performance lasts approximately twenty-two minutes.

String Quartet No. 14 is the one of a series of seventeen works in the medium by the Brazilian composer Heitor Villa-Lobos, and was written in 1953. A performance lasts approximately seventeen minutes.