Phrase and Form · Lesson 1
Motives and Phrases
about 15 min
What this lesson is for
A piece is not born whole; it is assembled from small units. The smallest is the motive, and a group of motives makes a phrase.
- Explain a motive as the smallest unit that loses its identity if divided further
- Distinguish the transformations of a motive - repetition, sequence, inversion, augmentation and diminution
- Define a phrase as a unit delimited by a cadence
- Explain why two- and four-measure lengths became standard, in terms of metrical hierarchy
In this lesson
The seven units so far have all concerned the near view, vertically and horizontally — the contents of one chord, the join between two chords, the motion of a few melodic notes.
From here the camera pulls back to ask how those assemble into the shape of a piece. That hierarchy is the subject of formal analysis.
Pieces are built by nesting
Language has letters, words, sentences, and paragraphs. Music has an equivalent hierarchy.
| Unit | Typical length | What delimits it |
|---|---|---|
| Motive | 1–2 measures | dividing it further destroys its character |
| Phrase | 4 measures | a cadence |
| Period | 8 measures | a pair of half and authentic cadences |
| Section | 8–32 measures | a conclusive cadence and repeat signs |
This lesson takes the lower two, motive and phrase.
Motive — the smallest unit that survives division
A motive is the smallest unit combining melody and rhythm. Break it down further and its character is gone.
Length does not define it. Two notes can be a motive. The opening of Beethoven’s Fifth Symphony is four notes — the same pitch three times, then a drop. Those four notes recur, transformed, across the entire movement.
For a motive to function as one, a single condition has to hold: it must be recognizable when it returns. Four notes heard once are just four notes. Repetition is what makes them a motive.
Four ways to transform a motive
Repeating a motive verbatim gets tiresome. Music extends material by transforming it, and four techniques account for most of it.
| Transformation | What changes |
|---|---|
| Repetition | nothing; it recurs as it was |
| Sequence | the pitch level, with the shape preserved |
| Inversion | the direction; what rose now falls |
| Augmentation / diminution | the note values lengthen or shorten; the melodic shape is unchanged |
One motive, four transformations
Check: All of these derive from the four-note figure in Fig. 1. The first is unchanged, the second is moved up a step, the third flips the contour, and the fourth doubles the note values. The pitches differ and yet all four register as relatives of one another. That sense of kinship is what makes musical form possible.
the material itself
Check
A motive returns with its contour turned upside down. What is this transformation called?
Phrase — the unit a cadence delimits
Motives group into phrases. The standard length is four measures.
The essential point is that a phrase is delimited by a cadence, not a barline. Barlines exist for counting beats and are drawn at even intervals regardless of meaning. Where a phrase ends depends on whether the harmony has produced a division.
The cadences from Unit 4 become the tool for segmenting structure here.
A four-measure phrase, with and without closure
Check: The first arrives on V in the fourth measure and stops. A half cadence divides while leaving things unfinished. The second follows the same three measures and returns to I. The authentic cadence makes it unmistakable that a section has closed. Same length; the final chord changes what the phrase means.
I – IV – ii – V
Why four measures
Four measures is a convention, but not a groundless one. It follows from the nesting of metrical accent.
Unit 0 established that beats carry strong and weak accents in alternation. The same thing happens between measures. Pair two measures and the first feels strong, the second weak. Put two such pairs together and the first pair feels strong, the second weak.
Because that nesting continues, lengths that are powers of two — two, four, eight, sixteen measures — are heard as units without effort. Four is not special in itself; being a power of two is what matters.
This is not an absolute rule. Three- and five-measure phrases genuinely exist, and adding or removing a measure to defeat expectation is a standard device. The defeat works only because the listener was expecting four.
Check
You have written a six-measure phrase. Is that a mistake?
Phrases do not have to begin at a barline
One more thing that trips people up when analyzing real music: a phrase does not necessarily begin at the start of a measure.
Starting on the last beat of a measure and landing on the downbeat of the next is an anacrusis, or pickup.
With a pickup, barlines and phrase divisions no longer line up. A four-measure phrase ends up written across five measures on the page.
Songs with lyrics use this constantly, because sentences do not reliably begin on a stressed syllable. “Tomorrow” starts weak and puts the weight on the second syllable; following the natural stress of the words produces a melody with a pickup.
When analyzing, listen for where the downbeats fall rather than counting barlines. The positions of the cadences from earlier units are likewise judged against downbeats, not barlines.
From motive to phrase
Real phrases are assembled by lining up several motives. A common construction is to state a two-measure motive and then add two more by transforming it.
That produces four measures, and placing a cadence at the end completes one phrase. The next lesson combines two phrases into a period.
See phrase divisions in the form viewer Choose the parallel period and use the play-this-section control to hear the first and second halves separately. The division becomes audible Form Viewer → Build a motive and transform it in the step sequencer Enter a four-note motive, then re-enter the same shape at a different pitch level to produce a sequence Step Sequencer →A motive is material; a phrase is one sentence made from it. The next lesson covers how two sentences combine into a question and an answer.
Exercises
Every answer here is cross-checked against the theory engine. Work them out before you grade.
- 1
Which is the best definition of a motive?
- 2
A motive is repeated in the same shape a step higher. What is this transformation called?
- 3
What determines where a phrase ends?
- 4
A phrase in C major ends with the two chords Dm and G. How does it close?
- 5
What best explains why four-measure phrases became standard in Western music?
Before you move on
Check that you can explain each point above in your own words.