Period
A two-phrase structure, typically an antecedent answered by a consequent
Related
A period is usually built from two phrases: an antecedent proposes something unfinished, and a consequent takes it up and closes it. The antecedent often stops on the dominant, forming a half cadence that leaves the ear suspended; the consequent returns to the tonic and lands on an authentic cadence. The two phrases frequently share a beginning and differ at the end, like a question and its answer. This is the most common and most audible phrase structure in Classical music.
A period is not simply "two phrases". A real period requires the second phrase to answer the first: the material must correspond, the harmony must close, and the lengths are often balanced. Two independent phrases that do not respond to each other are merely successive phrases, not a period. A period can also be expanded: a continuation may be inserted after the antecedent, the consequent may be extended, or the closing may be stretched. In sonata form the period is a basic building block of the thematic group.
The common misconception is to confuse period with phrase, or to assume that any two phrases make a period. A phrase is one sentence; a period is a relationship between sentences. Without answer, without harmonic response, there is only succession. Another misconception is that a period must be strictly symmetrical. Composers often use uneven lengths, varied cadences or expansion to avoid squareness and sharpen the question-and-answer tension. When hearing a period, listen to how the second phrase answers the first, not merely where it stops.
Sources
- 乐段与前句、后句的定义和类型，参 The New Grove Dictionary of Music and Musicians, "Period"；本文为原创表述
Used for fact-checking only; all prose is original.