Chamber music: musical compositions for ensembles of from three to eight instruments, traditionally performed without a conductor and usually written for performance in a room or reception hall before a small audience or indeed only for the pleasure of the players.

Chamber music could be said to have started with the madrigals and consorts of the 16th century. Most of the instrumental works consisted of fantasies, dances, and suites written in the late Renaissance and the early Baroque periods. Domestic music began to flourish in the aristocratic houses of England, Italy and Germany of the 17th century, and the musicians were often members of the household. During the 18th century, chamber music flourished in literary and artistic circle throughout Europe. Much of it consisted of solo and trio sonatas by such composers as Arcangelo Corelli, often for continuo instrument and strings. From this developed the classic trio with a much more prominent role for the pianoforte.

It was left to Joseph Haydn almost to invent the new form of the string quartet, which ideally reflected the 18th century's sense of classical form, with four instruments "conversing" on equal terms. Wolfgang Amadeus Mozart and Ludwig van Beethoven further enhanced the form and -- with Haydn – gave chamber music the status it has today. They poured their most sustained invention and their most profound ideas into their quartets (and in Mozart's case, quintets). Works written at this time for mixed ensembles were usually lighter in character, and indeed were often termed serenades or divertimenti.

As the 19th century progressed not only did composers such as Franz Schubert, Robert Schumann, Felix Mendelssohn, Johannes Brahms, and Antonin Dvorak add immeasurably to the store of chamber music, but it was also being performed more and more frequently in public. Professional quartets came into being to fulfill demand for public performance, though amateurs continued to perform chamber music in the drawing room.

In the 20th century, the repertory has been further enriched by Maurice Ravel, Claude Debussy, Bela Bartok, Dmitry Shostakovich, and Benjamin Britten among others, and the genre shows no sign of languishing even in a musical world often more concerned with experimental forms. This century has also seen a renewal of interest in combining the voice with chamber groups. Arnold Shoenberg, Ralph Vaughan Williams, Gustav Holst, and more recently, Pierre Boulez and Maxwell Davies have shown interest in adapting the form to their somewhat esoteric needs. The technical difficulty of most recent chamber music has taken it outside the range of the most amateur player in the home, but chamber groups nevertheless continue to perform the classical repertory enthusiastically for small groups in the private house.

Chamber music particularly, the quartet is still considered by many persons to be the "purest" form of music by virtue of its ideal balance of instruments. Because it is still often performed for pleasure by small groups of people, it probably gives the most lasting pleasure to more music lovers than any other kind of music.