String quintet

As an extension to the string quartet (two violins, a viola, and a cello), a string quintet includes a fifth string instrument, usually a second viola (a so-called "viola quintet") or a second cello (a "cello quintet"), or occasionally a double bass.

Notable examples of classic "viola quintets", in four movement form include those of Wolfgang Amadeus Mozart.

Other examples were written by composers including Johannes Brahms and Felix Mendelssohn.

The term string quintet may refer to a group of five players that performs such works.

The ensemble was standard in 17th century Italy and can be seen as early as 1607 in Claudio Monteverdi's opera, L'Orfeo.