Sonata form was the most important principle of musical structure during the classical period, and has remained so up to the present day. It applies most often to a single movement, part of a sonata, symphony or quartet, but an independent movement, such as an overture, may also be in sonata form. Its principles affect the structural features of other works, including the Mass. Sonata form is most clearly seen as the expansion of the binary form of Baroque dances, but other genres, including the aria and the concerto, also influenced its development. Essentially, sonata form presents and develops contrasting musical ideas at length, while providing a convincing unity to the whole. Examples of the form can be found in the works of Haydn, Mozart and Beethoven.

A typical sonata-form movement consists of three main sections, based on a two-part key structure:

1. Exposition. This opening section sets out the main themes of the movement. It is divided into a first-subject group in the tonic and, after transitional material, a second-subject group in another key, usually the dominant in major movements (the relative major in minor movements). A short codetta, reinforcing the new key, often rounds off the section.

2. Development. In this section, music from the exposition is treated in a variety of ways. The themes may be fragmented or treated contrapuntally, or be the basis of new ideas; they usually move through a number of keys and create rhythmic and melodic tensions.

3. Recapitulation. In this final section both main themes are repeated, usually both in the home key, thus resolving the tension created by the dominant (or relative major) in the exposition. There may also be temporary visits to other keys, but the return of the original material in the home key marks the culmination of the movement. To the three-section structure of sonata form a slow introduction and a coda may also be added.

Another form used frequently in the classical era was the sonata-rondo. As its name suggests, it combined the idea of the sonata (in which the tension created by presenting thematic material in two keys is resolved by restating the themes in the home key) with that of the rondo (in which a main section recurs between subsidiary sections). The tonal plan of sonata form is thus combined with the thematic structure of the rondo.

Styles & Forms | Classical Era | Classical
Inside the Music | Dissonance | Classical Era | Classical