Ezra Pound, in his essay "A Retrospect," uses the term "musical phrase" in one of the three principles that he explains characterize his particular school of poetry. Here is the full principle as it appears in the essay:

As regarding rhythm: to compose in the sequence of the musical phrase, not in sequence of a metronome.

A metronome is a device that ticks in a regular pattern. Pound explains that the "musical phrase" is a better way to think about grouping and arranging words in a poem, rather than abiding by expected and regular patterns of sound. He discusses the musicality of words and poetry later in the essay, reinforcing the notion that the musical rolls and waves of words in a poem are much preferred to the repetitive rhythm of words that imitate the sequence of a metronome.

One of Ezra Pound's three principles of Imagism was

As regarding rhythm: to compose in the sequence of the musical phrase, not in sequence of a metronome.

This principle was concerned with prosody. Pound was strongly interested in the different forms of possible rhythmic arrangements for verse, especially those of the troubadours and the early Anglo-Saxon and Italian poets. He saw the fluidity and musicality of their rhythms as more interesting than what he considered the metronomic regularity of much of Victorian verse. In many ways, he was part of the free verse movement that began in France in the fin de siecle, although his actual practice often was closer to extreme variations on a theme than what late–twentieth-century poets would term pure free verse.