Period

A period is a musical unit of two phrases: an antecedent, which ends on a weaker cadence, usually a half cadence, and a consequent, which answers it and closes on an authentic cadence. A typical eight-bar period in C major might run I to V in bars one to four, then I to IV to V to I in bars five to eight. Periods can be parallel, where both phrases begin with similar material, or contrasting, where the consequent begins differently. Many Classical themes are built as periods. The period is a basic unit of phrase structure, and recognising it helps identify where a melody divides into its phrases and where the harmony closes.

Related terms

• SentenceAn eight-bar phrase structure of a presentation, which states a basic idea, followed by a continuation that accelerates toward a cadence.
• PhraseA unit of melody or harmony, usually around four bars in tonal music, that ends with a cadence and forms a complete musical thought.
• Half cadenceA cadence that ends on the dominant chord, so the phrase pauses and asks for a continuation rather than resolving to the tonic.
• CadenceA conventional pattern at the end of a phrase or section that gives a sense of closure, pause or continuation.