a musical form that is used for the first movement of a sonata, symphony, concerto, etc and consists basically of an exposition, a development, and a recapitulation in which usu two themes are introduced, developed, and then repeated
The preeminent instrumental form of the 18th, 19th and early 20th cents, sonata form relies upon the contrast between two musical keys (conventionally tonic and dominant). Classical sonata form is built on two main themes and consists of three parts – an exposition that begins with the first theme in the tonic and moves to the dominant for the statement of the second, a development that develops the two themes, often ranging through a variety of keys, and eventually a return to the tonic for the recapitulation in which both themes are heard in the tonic key. As the form evolved, however, the archetype was subjected to far more elaboration — Andrew Clements