The poem begins with alliteration, as the speaker repeats the breathy /h/ sound in the first line:
I hear the halting footsteps of a lass
This gives the poem's opening line a soft, breathy tone that almost makes it sound like the speaker is covertly whispering in a dark alley.
As the poem goes, the speaker's use of alliteration grows less gentle and soothing. Take lines 4 and 5, for example, when the speaker alliterates using the heavy /b/ and /d/ sounds:
To bend and barter at desire's call.
Ah, little dark girls who in slippered feet
This blunter alliteration makes the speaker's language feel more forceful. The percussive solidity of the /b/ and /d/ sounds also calls attention to the words "bend," "barter," "desire," and "dark," inviting readers to envision these women stooping to speak to potential clients who sit in cars and seem to embody lust itself.
The speaker also uses alliteration to add intensity to passionate moments. This is the case in lines 13 and 14, when the speaker alliterates the /w/ and /d/ sounds while lamenting the world's cruelty:
Ah, stern harsh world, that in the wretched way
Of poverty, dishonor and disgrace
The repetition of the /w/ and /d/ sounds once again adds a certain rhythm to the poem, making it feel musical and melodic while also giving it a slightly forceful edge. The thudding rhythm created by the /d/ sound in the phrase "dishonor and disgrace" is particularly striking, giving the line a strong pulse that adds power to the speaker's overall tone. Alliteration, then, helps the speaker convey a sense of frustration.