Music is a language and, like any language, it organizes its discourse into larger and larger units. Just as letters form words, words form sentences and sentences form paragraphs, in music sounds are grouped into motives, sub-phrases, phrases and periods. Understanding this hierarchy, the syntax of music, is the basis for analyzing any piece.
The analogy with language
The simplest way to understand these units is to compare them with the units of spoken language:
| In language | In music | What it is |
|---|---|---|
| Word | Motive (the smallest unit) | The smallest unit with a meaning of its own. |
| Phrase (grammar) | Sub-phrase (half phrase) | Half a musical idea; half of a phrase. |
| Sentence | Phrase | A complete musical idea, closed by a cadence. |
| Paragraph | Period | Phrases linked together. |
The hierarchy, from small to large
Motive
This is the smallest cell with musical meaning of its own, the “word” of the discourse. It usually takes up one or two measures (UK: bars) and is often repeated or transformed throughout a piece. The famous “short-short-short-long” figure that opens Beethoven’s Fifth Symphony is a motive. (Spanish-language texts call it an inciso.)
Sub-phrase
Joining two or three motives forms a sub-phrase: half of a musical idea. On its own it feels incomplete, as if “waiting” for a continuation. It is normally half of a phrase (about two measures). English-language books often call this unit a “phrase segment” or “half phrase”; the term “sub-phrase” is used here.
Phrase
The phrase is the basic unit of musical discourse: an idea that makes complete sense and almost always ends with a cadence. It results from joining two sub-phrases and often lasts four measures.
Period
The period links phrases together, the “paragraph” of music. The most typical case is an eight-measure period made of an antecedent phrase, which ends with a feeling of suspension (for example, on a half cadence), and a consequent phrase, which ends firmly with an authentic cadence.
How an 8-measure period nests
This diagram shows how the small units fit inside the large ones:
| Period · 8 measures | |||||||
| Antecedent phrase | Consequent phrase | ||||||
| Sub-phrase | Sub-phrase | Sub-phrase | Sub-phrase | ||||
| Motive | Motive | Motive | Motive | Motive | Motive | Motive | Motive |
How a phrase is classified
Besides its length, a phrase is described by how it begins and how it ends in relation to the strong beats of the measure:
- The beginning: on the downbeat, on a pickup, or on an off-beat after a rest, depending on where the first note falls.
- The ending: on a strong beat or on a weak beat, depending on where the last note falls.
Do not confuse this rhythmic ending with the cadence, which is the harmonic ending of the phrase: the chord progression that closes it.