Sonata Form is a three-part musical structure of exposition, development, and recapitulation.
Sonata form is a structural template that dominated instrumental composition from the mid-18th century onward, organizing a movement into three principal sections: an exposition that introduces two contrasting musical themes (often in two different keys), a development that fragments, transforms, and recombines that material through a sequence of harmonic tension, and a recapitulation that returns both themes home, now resolved into a single key. The form gave Classical-era composers — Haydn, Mozart, and later Beethoven — a shared architecture flexible enough to sustain an entire symphony's opening movement, yet rigorous enough that a listener could feel departure, conflict, and return even on a first hearing. Beethoven in particular treated sonata form's boundaries as something to stretch and provoke rather than obey, expanding development sections into the dramatic centers of his symphonies and previewing the more radical formal experiments of the Romantic era that followed.