The theory in brief
William E. Caplin (McGill University), in Classical Form (Oxford, 1998) and Analyzing Classical Form (2013), develops ideas of Schoenberg and Ratz and proposes that every group of bars in Classical music (Haydn, Mozart, Beethoven) has a formal function: it tells the listener whether they are at the beginning, in the middle or at the end of a unit. The functions are recognized by harmonic, melodic and rhythmic signals, and combine into a few theme types. It is today the standard model for teaching Classical form in composition and analysis courses.
The temporal functions
| Function | Typical signals | Examples |
|---|---|---|
| Beginning | tonic prolongation, basic idea presented and repeated, slow harmonic rhythm | presentation, antecedent, main theme |
| Middle | instability: fragmentation, sequences, acceleration of harmonic rhythm, unstable keys | continuation, contrasting middle, development |
| End | cadential progression (I6–IV–V–I, ii6–V–I) and cadence | cadential function, closing group |
| Framing | before the beginning (introduction) or after the end (codetta, coda) | slow introduction, codettas, post-cadential |
Theme types (phrase level)
- Sentence: presentation (basic idea 2 + repetition 2) → continuation + cadence (4). See the dedicated entry.
- Period: antecedent (basic idea + contrasting idea → half cadence) → consequent (basic idea + contrasting idea → perfect cadence). See the dedicated entry.
- Hybrids (Caplin identifies four main ones):
- Antecedent + continuation: begins like a period (bi + ci), but the second half does not repeat the beginning, it fragments and cadences.
- Antecedent + cadential: after the antecedent a long cadential progression arrives right away.
- Compound basic idea + continuation: the first half (bi + ci without cadence) prolongs the tonic, then a continuation.
- Compound basic idea + consequent: like a period whose antecedent does not cadence.
- Compound themes (16 bars): compound period (antecedent = 8-bar presentation + continuation with half cadence; consequent the same with perfect cadence) and compound sentence (8-bar presentation, 8-bar continuation).
- Small ternary (a a′ b a′′, with a′ often repeated) and small binary: the themes of minuets, rondos and variations.
Functions at the movement level
In a sonata form Caplin distinguishes:
- Main theme: "tight-knit" structure: stable key, clear perfect cadence, conventional theme type.
- Transition: destabilizes the tonic, modulates (or not) and ends with a half cadence, often followed by a "standing on the dominant" (dominant prolongation).
- Subordinate theme: "loose" structure: extensions, expansions of the cadential progression, evaded, deceptive or abandoned cadences, the "one more time" repetition of the last phrase before the definitive perfect cadence.
- Closing section: codettas after the cadence that closes the subordinate theme.
- Development: pre-core, core (model–sequence–fragmentation), retransition over a dominant pedal.
Analysis example (C major, 8-bar theme)
- mm. 1–2: basic idea C–E–G–E | D (I – V)
- mm. 3–4: basic idea repeated over the dominant (V – I): presentation (beginning function).
- mm. 5–6: one-bar fragments in sequence (IV – ii – V/V): continuation (middle function).
- mm. 7–8: I6/4 – V7 – I: cadential (end function).
If instead mm. 3–4 ended with a half cadence (bi + ci → V) and mm. 5–8 fragmented and cadenced, you would have the antecedent + continuation hybrid.
Why it is useful to a producer
The concepts of "tight-knit" and "loose" also hold in pop: the verse is often tight-knit (repeated loop), the pre-chorus has a middle function (fragmentation, acceleration, dominant pedal = "standing on the dominant"), the chorus is beginning and end function at once, and the post-chorus has a post-cadential function. Thinking in functions helps you write sections that "sound like" what they are supposed to be.
Exercise
Analyze the first 8 or 16 bars of three themes: Mozart, Sonata K. 545, I; Beethoven, Sonata op. 2 No. 1, I (a textbook sentence); Mozart, "Eine kleine Nachtmusik" K. 525, I. For each bar write the function (presentation, continuation, cadential) and the theme type.
Related topics
The sentence, The period, Sonata form, Sonata form: Hepokoski and Darcy's Sonata Theory, Cadences, Harmonic rhythm.