A string quartet is a form of instrumentation in Western music tradition that consists of two violins, a viola, and a cello playing a multi-movement musical composition utilizing the sonata form. Another common instrumentation is the piano quartet, consisting of violin, viola, cello, and piano. The 'quartet' is a type of chamber music popular beginning in the 18th century, when public concert-giving began, towards present day, and is considered the most important form in chamber music. One of the first contributors, Luigi Boccherini, wrote 100 string quartets. Other important contributors are Franz Joseph Haydn, Mozart, and Ludwig van Beethoven.
The particular choice and number of instruments derives from the registers of the human voice: soprano, alto, tenor and bass. 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. In opera a quartet refers to the use of four voices.
Many believe the four instrument arrangement to be one of the most difficult to compose for compared with a trio or quintet[?], for instance. It is suggested that the difficulty arises from the complex interplay of four distinct voices performing under large temporal and tonal constrasts. Many of the performers find it one of the most ejoyable of performance arrangements, allowing each player to perform their own distinct part, rarely playing a "background" or "blending" part, important only in connection to the larger whole.
Later, in musical styles outside of the classical forms, many artists use the four part instrumentation such as in jazz saxophone quartets, guitar quartets, horn quartets, and barbershop quartets[?]. The quartet form is constantly maturing and experimented with and is still in popular use.