A piece of music, almost invariably instrumental and usually in several movements, for a soloist or a small ensemble; or a structural principle, the sonata form.

16th and 17th Centuries

In the late 16th century numerous terms were used for instrumental pieces, one of which was 'sonata', indicating something played as opposed to something sung ('cantata'). Until circa 1650 it was used interchangeably with 'canzona'. Around 1600 Giovanni Gabrieli popularized a type of sonata for two or more instrumental groups, but he also pointed to the future meaning of the word in his "Sonata per tre violini" (1615).

In the early phase the forms are single-movement or multi-sectional, in the manner of the canzona. The single-movement sonata survived later in the era in such byways as G.C. Arresti's anthology of 18 "Sonate de organo" (circa 1700) and the keyboard sonatas (or 'toccatas') of Seixas, but by the time of Corelli (1653-1713) the sonata usually consisted of a number of separate movements.

Corelli was largely responsible for establishing the slow-fast-slow-fast order of movements in the Sonata da chiesa (church sonata). He used it in most of his trio sonatas opp.1 and 3, but added a fifth movement in his solo church sonatas op. 5. The order of movements in the Sonata da camera ('chamber sonata') was less standardized, but many examples follow the order of the four main dances of the Baroque suite: allemande, courante, sarabande, gigue. More often the "chiesa" and "camera" types cross or even fuse, as in the earliest published sonatas of Telemann and Vivaldi.

In the late Baroque there is greater standardization both of the cycle and of individual movements, whether in the more conservative, motivic styles like Bach's, which still lead to fugal types of form, or in the more progressive, homophonic ones of composers like Tartini or Leclair, which lead to the newer rondo, the ternary A B A form and similar sectional, integrated designs.

As far as instruments are concerned, the main Baroque type was the trio sonata, especially that for two violins and continuo. In addition to those of Corelli, Handel and Bach, the 22 sonatas of Purcell are outstanding among the trio type (though the cello part is sometimes independent of the continuo). After 1700 the 'solo' sonata, for one melody instrument and bass, became more popular; violin, flute, oboe and cello were the most favored instruments. More exceptional were sonatas for unaccompanied solo instruments, such as Biber's and Bach's for violin, Handel's for harpsichord and Bach's for organ.

18th Century

A significant starting point for the Classical period (circa 1735- circa 1820) is the sudden flowering of the solo keyboard sonata with Domenico Scarlatti, Alberti and C.P.E. Bach. As the clavichord and harpsichord were superseded by the piano, the keyboard sonata continued to rank high in the works of Haydn, Clementi, Mozart and Beethoven. Just as numerous, but of less artistic and historical importance, were the 'accompanied sonatas' for keyboard, usually with violin (sometimes optional). Only towards the end of the period, in the mature violin sonatas of Mozart and Beethoven, and in the latter's cello sonatas, are string and keyboard instruments treated as equals.

There is no consistent trend in the number and order of movements. The three-movement sequence, fast-slow-fast, predominates; a fourth is often present, but its character and placing vary. The so-called 'Italian plan' in two movements, usually both fast or one fast and one moderate, occurs in about half the sonatas of the main Italian composers from Alberti to Boccherini, and the single-movement keyboard sonatas of the three notable pre-Classical composers in Iberia - Seixas, Scarlatti and Soler - are often paired by key in the source manuscripts.

The first movement of Classical sonatas is most often in Sonata form. The slow movement may also approximate to sonata form, though usually with less development and a more simple phrase structure; other common forms include A B A or A B designs, rondos, variations and free fantasias. Among forms used for inner and final movements are the minuet or scherzo, the rondo or sonata-rondo and variations.

19th Century

The sonatas of the Romantic period (circa 1790- circa 1915) exemplify the rich variety of national and personal styles that characterize that era. As far as structure and basic approach are concerned, they fall into two categories. To the first belong the sonatas of Schubert, Weber, Chopin, Schumann, Brahms, Grieg, Fauré and Franck, which expand the Classical three- or four-movement form but do not break with it. While rarely achieving the logic or fluent rhythmic organization of the high Classical masterworks, they often sought a more positive organization of the cycle of movements. The 'basic motif' in Brahms' Violin Sonata op. 78 and the 'cyclical procedures' in Franck's Violin Sonata represent conscious methods of tying the movements together. Among sonatas in the smaller second category are those based on a programme, like Liszt's "Après une lecture de Dante, fantasia quasi sonata", or those which experiment with structure, such as the same composer's single-movement Piano Sonata in b Minor.

(See also Romantic Piano Literature)

20th Century

While traditional sonata structures have served the expressive purposes of many 20th-century composers, including Prokofiev and Shostakovich, the distinctiveness of the genre has during this time all but disappeared. The title no longer necessarily implies a work in several movements, one or more of them in sonata form, for piano alone or with another instrument. The break with tradition is evident both in those sonatas by Bartók, Stravinsky, Poulenc and Hindemith which look back to a much earlier age and in the piano sonalas of Barraqué and Boulez, which have no links of form or genre with any previous Sonatas.