Phrases, cadences and form letters
Form is the plan or shape of a whole piece. It tells us which parts repeat and which are new.
Building blocks
- Motif: a tiny idea of a few notes.
- Phrase: a musical sentence, often 4 bars long.
- Cadence: the ending of a phrase. An imperfect cadence sounds unfinished (a comma). A perfect cadence sounds finished (a full stop).
- Question and answer: two phrases where the second one answers the first.
Letters
We name each part with a letter. A new letter means new music. A small number (A1) means the same part, slightly changed.
Form balances repetition (unity, easy to remember) and contrast (interest, surprise).
Instrumental forms: binary, ternary, rondo, variations, sonata
- Binary (AB): two parts, often each repeated (AABB). Common in Baroque dances.
- Ternary (ABA): A returns after a contrasting B. Used in the minuet and trio and many slow pieces.
- Rondo (ABACA): a main theme returns between episodes. Often a lively last movement.
- Theme and variations (A A1 A2…): one theme changed by rhythm, key (major/minor), speed, ornaments or instruments.
- Ground bass / ostinato: a short bass line repeats again and again while the music above changes.
- Sonata form: exposition (two themes, two keys), development (themes broken up and moved through keys), recapitulation (themes return, now in the home key), sometimes a coda (ending).
Large instrumental genres
A sonata (one or two players), symphony (orchestra) and concerto (soloist + orchestra) usually have 3 or 4 movements, often fast – slow – (dance) – fast. A suite is a set of dances.
Dances and vocal genres
Dance forms
Dances have a steady metre and clear repeated sections. Examples: the minuet (graceful, 3 beats), waltz (3 beats, strong first beat), march (2 or 4 beats), gigue (quick, lively), tango, and folk dances such as bhangra or the polka.
Song forms
- Strophic: the same music for every verse (hymns, folk songs).
- Through-composed: new music for each part, following the story of the words.
- Verse–chorus: verses change the words, the chorus repeats; often with intro, bridge and outro.
- 12-bar blues and 32-bar song form (AABA) in jazz and popular music.
Large vocal genres
Opera (a drama sung on stage, with arias and recitatives), oratorio (a sung story, not acted), mass, cantata, art song and the musical.
How to analyse form when you listen (Try it)
- Listen for the first main tune. Call it A.
- Each time something new starts, give it the next letter.
- When an old tune returns, use its letter again. If it is changed, add a number (A1).
- Listen for cadences: they mark where sections end.
- Write the string of letters, for example A B A C A, and name the form.
Try it: take a song you know well. Write V for verse and C for chorus as you listen. Is it V C V C B C? Then use the picker in the 3D and compare.
Key formulas and definitions
- Form = the plan of a piece
- Binary = A B
- Ternary = A B A
- Rondo = A B A C A
- Theme and variations = A A1 A2 A3
- Sonata form = Exposition + Development + Recapitulation (+ Coda)
- Strophic = same music every verse
- Verse–chorus = V C V C (bridge) C
Worked examples
1. A piece goes: tune 1, tune 2, tune 1, tune 3, tune 1. Name the form.
Label: A B A C A. The main tune returns between new parts, so it is a rondo.
2. A song has 4 verses, each with new words but the same melody. Name the form.
The music repeats for each verse: A A A A. This is strophic form.
3. A piece in ternary form has sections of 16, 8 and 16 bars in 4/4. How many beats is it?
Total bars = 16 + 8 + 16 = 40. Beats = 40 × 4 = 160 beats.
Common mistakes
- Thinking a new letter means a new piece. It only means new music inside the same piece.
- Confusing rondo with ternary: ternary has one contrast (ABA), rondo has two or more (ABACA).
- Thinking sonata form and a sonata are the same thing. Sonata form is the plan of one movement; a sonata is a whole work.
- Forgetting that a changed return keeps its letter with a number (A1); it is not a new letter.