How does binary form relate to the origins of sonata form?

Sonata form is often described as a complex evolution of the binary form that was prominent in 17th- and 18th-century music. While sonata form consists of three parts—exposition, development, and recapitulation—it is fundamentally rooted in the two-part structure of binary form.1

In binary form, the structure relies on the interrelationship of tonalities or keys. The first section moves from the home key to a new key, while the second section begins in that new key and returns to the original home key. Sonata form mirrors this harmonic motion: the exposition corresponds to the first part of binary form, while the development and recapitulation together correspond to the second part.12

Because of this lineage, sonata form is sometimes designated as "compound binary form". This term highlights its origins while acknowledging its added complexity, as sonata form treats musical themes dialectically—combining, breaking up, and recontextualizing them—rather than simply relying on the melodic-rhythmic links typical of earlier binary structures.12