Binary (AB)
Two sections, usually repeated: ||: A :||: B :||.
- In major, A goes from the tonic to the dominant (C → G), B returns from the dominant to the tonic.
- In minor, A often goes to the relative major (A minor → C major).
- Rounded binary: at the end of B the opening material of A returns in the tonic. It is the ancestor of sonata form.
Typical of Baroque dances (allemande, courante, minuet).
Ternary (ABA)
Three sections: A complete and closed in the tonic, B contrasting (key, character, texture), A repeated (often identical, “da capo”). Examples: da capo aria, minuet with trio (minuet – trio – minuet), nocturnes.
AABA song form (32 bars)
Four 8-bar sections: A – A – B (bridge, “middle eight”) – A. The B brings harmonic contrast (often on IV or a nearby key). It is the form of the Great American Songbook and of much 1960s pop.
Example in C
- A: | C | Am | F | G | C | Am | Dm G | C |
- B: | F | F | Em | Am | Dm | Dm | G | G7 |
- A: as above.
Real-world example
“Over the Rainbow” (Arlen, 1939) is a 32-bar AABA; the Minuet in G major attributed to Petzold (from the Notebook for Anna Magdalena Bach) is a simple binary form.