The Phrase. Part 1
A phrase is a substantial musical thought usually ending with a harmonic, melodic, and rhythmic cadence. The presence of a cadence distinguishes a phrase from a motive. Phrases are frequently four measures long, but may be longer or shorter. A phrase presents a complete (though sometimes dependent) musical thought.
Phrases frequently contain slight melodic interruptions and thus divide into two phrase members. Phrase members are sufficiently separated, usually by a longer note value or rest, to distinguish them as individual units. Sometimes the second phrase member is either a repetition or a sequence of the first; however, it is just as often contrasting.
Under certain conditions, phrase members may be nearly indistinguishable from phrases themselves, with only the tempo serving as the deciding factor.
Repeated phrases, whether identical or modified, are not typically regarded as period structures because the second phrase is not dependent on the first. Thus the antecedent– consequent concept does not apply.