Sonataallegro

Sonata-allegro form, commonly called sonata form, is a musical structure that became a dominant framework for the first movements of classical-era works, including sonatas, symphonies, and string quartets. It is organized into three principal sections—exposition, development, and recapitulation—with optional introductions and codas.

Exposition: introduces two contrasting themes, typically in different keys; the first theme in the home key, the second in a related key, with a bridging passage (transition) and a short closing section (codetta); the section is often repeated.

Development: forges and transforms motives drawn from the themes, frequently through modulation to distant keys and through chromatic or rhythmic techniques, creating tension that necessitates resolution.

Recapitulation: restates the main themes in the home key, providing tonal unity; a coda may follow to conclude.

Origins and evolution: The form matured in the Classical period, with prominent contributions from Haydn and Mozart; Beethoven extended and redefined its possibilities in the early Romantic era. The form continued to be used and adapted by later composers, including in concertos and larger-scale works.

Notes: While called 'sonata' or 'sonata form', the term does not imply a specific tempo; movements labeled Allegro are often structured in this form, but the form is independent of tempo.