Small ternary form
“Small ternary” is really where I kinda blur the lines between small structure form vs. large structure form. It’s basically ternary form but with phrases. It’s an ABA structure.
caplin-1998 (p.71, par.1) describes it as “one of the most important forms in all of classical instrumental music”.
Structure
In classical music
The first A section is the exposition. It should end with either a half cadence or an authentic cadence.
The B section is the contrasting middle. It should be similar but create contrast with the preceding A section. It should also end with a half cadence. (Dominant harmony is common to move to here.)
The second A section is the recapitulation. It may not be an exact repetition of the original A section: some material may be cut.
Both the A and B sections can utilize different kind of small structure forms in themselves. For example, the A section could be a period and the B section could be a sentence.