Sonata form is the grandest achievement of the Classical era. Its principle is the drama of contrast: two themes (primary and secondary) in different keys first appear as opposites and, by the end, are reconciled.
This form underlies the opening movements of symphonies by Haydn, Mozart, Beethoven, Brahms, and Mahler. In the 20th century, composers reimagined it: Bartók kept the scheme but infused it with new harmony; Hindemith gave it rigorous logic; and later composers turned it into a space where styles from different eras collide.
Sonata form consists of three main sections: the exposition (a statement of the primary and secondary themes in different keys), the development (the conflicting growth of the themes), and the recapitulation (the return of both themes in the home key). A slow introduction often precedes them, and a coda rounds them off. This form became the universal “language” of instrumental music and underlies thousands of sonatas, symphonies, quartets, and concertos.
