Binary form—the division of a unit of music into two sections, either because (1) there are two periods (2) there are two repeated sections (“two-reprise form”).
Typical harmonic plans:
Typical sources of contrast early in the second section
- Motivic development (transformations and fragmentation)
- Modulations (other than to V or III)
- Pedal points (usually ^5 to set up a return of ^1)