A short piece presents a 16-bar melody (A), then 16 bars of contrasting material (B), then returns to the opening melody (A). This structure is best described as:
ABinary form (AB)
BTernary form (ABA)
CSonata form
DRondo form (ABACA)
Ternary form (ABA) is defined by its three-part structure: an opening section, a contrasting section, and a *return* to the opening material. The return is the key feature that distinguishes ternary from binary form — binary form (AB) does not bring back the A material. Sonata form also begins and ends in the home key but has a development section, not a simple contrast.
Question 2 Multiple Choice
What is the most important distinction between ternary form (ABA) and sonata form?
AIn ternary form, the middle section (B) introduces contrasting material; in sonata form, the development section works through and transforms the opening themes
BSonata form has three sections and ternary form has only two
CTernary form always modulates to a new key in the B section; sonata form stays in one key
DThe A section never repeats in sonata form, but always repeats in ternary
Both forms begin and end in the home key, which can make them superficially similar. The diagnostic difference is what the *middle does*: ternary form's B section contrasts (different material, different character) but does not develop; sonata form's development section fragments and transforms themes through a progression of unstable keys, creating far greater tension before the recapitulation. Option B is wrong — both forms have three functional sections.
Question 3 True / False
In binary form (AB), the A section often ends on a half cadence or a cadence in a related key, leaving the harmony unresolved before the B section.
TTrue
FFalse
Answer: True
This structural feature creates the forward momentum of binary form — the A section doesn't fully close harmonically, which propels the listener into the B section. The B section then resolves back to the tonic. This contrasts with ternary form's B section, which is more tonally complete and self-contained before the return of A.
Question 4 True / False
For a piece to qualify as ternary form, the return of the A section is expected to be an exact, note-for-note repetition of the opening material.
TTrue
FFalse
Answer: False
The return of A in ternary form can be ornamented, abbreviated, or varied — what matters is that the listener recognizes it as a homecoming, not that it is identical. Da capo arias are often performed with ornamentation on the return. The formal and perceptual criterion is recognition and resolution, not literal repetition. Requiring exact repetition is a common misconception that confuses exact recapitulation with formal structural return.
Question 5 Short Answer
How does listening to 'what the middle does' help you distinguish binary form, ternary form, and sonata form?
Think about your answer, then reveal below.
Model answer: Binary form has no true middle section — it simply moves from A to B with no return, so there is nothing to analyze in the middle. Ternary form's middle (B) introduces contrasting material, then gives way to the return of A; the middle's job is contrast. Sonata form's middle (development) takes themes from the exposition and fragments, modulates, and transforms them through unstable keys, building tension before the recapitulation restores the opening. If the middle contrasts, it's ternary; if the middle develops and destabilizes, it's sonata form.
Form analysis collapses if you only look at the beginning and end. Both ternary and sonata form begin and end in the home key with the opening material — but their middles are completely different in function. The middle section is the diagnostic section: contrast (ternary) vs. development (sonata). This principle extends to larger forms as well — form is always about what the middle does, not just the endpoints.