Sonata Form; Sonata-Allegro Form; First-Movement Form

The main form of the group embodying the 'sonata principle.' The most important principle of musical structure from the Classical period to the 20th century.  Sonata form applies to a single movement, most often part of a multi-movement work such as a sonata, symphony or string quartet; independent movements, e.g. an overture or tone poem, may also be in sonata form. The structure may be considered an expansion of the rounded binary form (A B a) familiar in Baroque dances, but other genres, including the aria and the concerto, also impinged on its development.
A typical sonata-form movement consists of three main sections.