binary form
A musical structure with two contrasting sections, AB.
In Depth
Binary form divides a piece into two complementary sections, labelled A and B. The A section typically moves from the home key to a related key, while the B section returns. Each section is usually repeated, giving the structure ||:A:||:B:||.
This form was the foundation of Baroque dance movements. Allemandes, courantes, sarabandes, and gigues in a Baroque suite nearly always use binary form. It also laid the groundwork for sonata form, which evolved from the expanded binary structures of the early Classical period.
Nearly every movement in a Baroque dance suite uses binary form, meaning a typical suite of six dances contains six pieces all built on the same two-part structure.