As your question shows, Claude McKay’s poem “Harlem Dancer,” which first appeared in his book of poetry Harlem Shadows (1922), is modeled at least in part after a Shakespearean sonnet. The rhyme scheme and end punctuation throughout this 14-line poem allow it to be broken up into four sections: three sections of four lines each (the quatrains) and one final section of two lines (the rhyming couplet). As is normally the case in Shakespearean sonnets, the rhyming couplet offers a summary or commentary on all that comes before it in the poem. In my view, that final commentary may prompt us to read the entire poem as including both a celebration of the performer and something along the lines of disapproval of the setting in which she performs.
The poem’s title and first quatrain identify the subject and set the scene. The poem probably takes place in a Harlem nightclub, and the unnamed “she” is dancing and singing before a mixed audience. While the opening lines’ references to “young prostitutes” and “half-clothed body” may suggest a certain seediness, the first stanza also likens the experience of watching the performer to something that might be experienced at “a picnic day” (that is, in daylight and out in the fresh, open air). The second stanza, which introduces the speaker’s own views, continues this seemingly incongruent imagery of the natural world (she is described as “a proudly-swaying palm”) even as it suggests that the current setting is less than ideal (it is “a storm”): “To me she seemed a proudly-swaying palm / Grown lovelier for passing through a storm.”
The imagery of the natural world does not continue into the third stanza; instead, the reader may be reminded here through the reference to “tossing coins” and the use of the word “devoured” that the performer is perhaps a prostitute herself. The speaker also turns attention away from the performer toward the “wine-flushed, bold-eyed” audience who do not seem to value her beauty as the speaker does. The closing couplet drives home this reservation or criticism: “But, looking at her falsely-smiling face / I knew her self was not in that strange place.” The naturalness or truth of her movements does not match the artificiality or falseness of the place of her performance.
The shift in the poem between lines 8 and 9 (the point at which the natural imagery ends) may allow us to appreciate the poem as a blend of the Shakespearean sonnet and Petrarchan sonnet.