A phrase is a stretch of music, usually spanning more than one or two measures, that forms a musically coherent unit. The musical term bears a close resemblance to the grammatical term. In both cases, the word phrase refers to an internally coherent unit, but it does not necessarily imply total closure or finality: just as a single grammatical phrase is not the same thing as a complete sentence, a single musical phrase is usually not sufficient to create a sense of musical conclusiveness. The “Yankee Doodle” example below is a case in point: it is coherent as a musical phrase, but it does not feel complete.
Yankee Doodle in C
Musicians use a combination of melodic, harmonic, and rhythmic considerations to determine what counts as a phrase as opposed to a smaller musical unit (such as a motive), or as a larger portion of a work’s form. One of the most important of these is the cadence, which signals the end of a phrase. For works that contain lyrics, the musical sense is often closely tied to the text, and this can be tremendously helpful in parsing music into its constituent phrases. In the example above, the textual phrase “Yankee Doodle went to town a-riding on a pony” is provided with a matching musical phrase; our sense that the text is incomplete (what did Yankee Doodle do in town?) is matched by a sense that the music, too, is unfinished, and will continue.