The String Quartet is an ensemble of four string players, consisting of one first and one second violin, a viola and a cello. It is the most important kind of chamber music group. The word quartet derives from French quart which means four. The players usually form permanent quartets, because they need to play together all the time in order to excel in performance. No one instrument dominates the others, all are equal, and the players must listen to each other very carefully. Players other than the first violinist get the tune often, so the music is fun for all four players. This ensemble is highly suited to playing intimate, subtle music, a strong contrast to the force and power of the orchestra.
Haydn is credited with the creation of the string quartet, so this ensemble is pre-eminent in the classical period. Previously, the harpsichord was alway used with other instrumental groupings, to play the basso continuo, or chord sequences read from a figured bass. Haydn did away with the harpsichord, allowing the clarity of music written for just 4 string instruments to shine through. He wrote over 70 works for this ensemble, and this category of music is also called a string quartet. Mozart, Beethoven, and Schubert all wrote many string quartets.
Much wonderful music has since been composed for string quartets in the romantic and modern periods also.