Sonata, a form of musical composition consisting of several independent movements, each of which is developed in accordance with certain accepted rules. The great body of instrumental music is based upon the sonata form. When first used, in the latter part of the 16th century, the word simply signified a composition for instruments, and conveyed no idea of any determined form. Gradually composers applied it to a composition for one or two instruments, consisting of three movements of contrasted character and time. Philipp Emmanuel Bach contributed greatly to the development of the sonata. His works of this class consisted of a first movement, allegro, a second, adagio, and a third, rondo, which was more vivacious than the others. Haydn adopted Bach's general plan, though in his 44 sonatas he developed the movements in a broader manner. Mozart and Beethoven composed some of their best works in this form; in their day it was the favorite kind of pianoforte composition. It has also been used by Von Weber, Schubert, Schumann, and other later composers.

Haydn added a fourth movement, the minuetto, and this, or its equivalent the scherzo, with the three previously existing movements, constitutes the form upon which all the quartet and quintet music for stringed instruments and the symphony are based.