Structure
A period is a musical phrase usually 8 bars long, divided into two halves of 4:
- Antecedent (bars 1–4): presents the idea and closes with a weak cadence, usually a half cadence on V. It is a question.
- Consequent (bars 5–8): starts like the antecedent and closes with a perfect authentic cadence on I. It is the answer.
Example in C major
- Antecedent: | C | F | C | G | (ends on V)
- Consequent: | C | F | G7 | C | (perfect authentic cadence)
The melody of bars 5–6 repeats that of bars 1–2; the ending changes.
Variants
- Parallel period: the consequent begins like the antecedent (the most common case).
- Contrasting period: the consequent has new material but closes the phrase.
- Modulating period: the consequent cadences in another key (in C, it closes on G).
- Double period: 16 bars, the strong cadence arrives only at the end.
In songwriting
Many pop verses are periods: two lines that end “open” and two that end “closed.” The same logic applies in rap to bars: four bars of question, four bars of answer.
Real-world example
The “Ode to Joy” (Beethoven, Ninth Symphony, 1824): the first four bars end on the second scale degree over the dominant (question), the next four start identically and close on the tonic (answer). It is a textbook parallel period.