rounded binary form
A binary form in which the opening material returns at the end of the second section, creating an A-B-A structure within two repeated halves
In Depth
Rounded binary form is one of the most common formal structures in Classical music and is the basis of most minuet, scherzo, and sonata-form movements. The first section (A) establishes the tonic and often modulates to the dominant. The second section begins with contrasting or developmental material (B) and then brings back the opening theme in the tonic (A), creating a satisfying sense of return. The form is written ||:A:||:BA:|| with both halves typically repeated.
Many of Haydn's and Mozart's minuet movements are in rounded binary form, and scholars now believe that sonata form evolved directly from this structure.