“She Walks in Beauty” was written to be set to music. What elements of the poem give it a musical quality?

"She Walks in Beauty" by Lord Byron has a very regular abab rhyme scheme, which gives the piece a lyrical quality. It adds repetition and a chorus/refrain-like rhythm to the poem, which allows it to be easily put to music and even sung. The poem contains three stanzas of six lines each.

In the first two stanzas, Byron often uses the literary technique of enjambment, which is when one line runs over without punctuation or pause into the next line. This technique creates an easy flow from one line to the next, also contributing to the lyrical nature of the poem. 

The meter of the poem is what most contributes to its musical quality. We've all heard of Shakespeare's famous iambic pentameter, which means that there are five stressed syllables per line usually alternating equally with unstressed syllables. However, Lord Byron uses iambic tetrameter - four stressed and four unstressed syllables per line. When one reads the poem out loud, it is easy to hear the beat of the piece. And when the meter changes like with line 4 "meet in her aspect," we know Byron is emphasizing the point of meeting.

Rhyme, enjambment and meter all contribute to both the meaning and the musicality of "She Walks in Beauty."