How does Langston Hughes create rhythm in the poem "Harlem"?

Langston Hughes' poem “Harlem” looks at the adverse, and potentially even catastrophic, effects of the lack of opportunity in some parts of American society.

Rhythm is the pattern created by the way the poet arranges words, stressed and unstressed syllables, punctuation, and sometimes even space. (There are more definitions for poetic rhythm, some quite complicated, but this will do for what we are talking about.)

One of the most obvious techniques Hughes uses to create rhythm in this poem is repetition. Usually we think of repetition as being the repeating of specific words, but in “Harlem,” Hughes is repeating “structure.” By that I mean he is repeating the same kind of sentence over and over again—a question. There are six questions in this short little poem. But Hughes doesn't just ask any old question in any old way—he constructs them carefully. Notice that he starts off with a fairly innocuous question:

What happens to a dream deferred?

This is a reasonable question; there's nothing shocking about it. But the succeeding questions refine the poet's focus, relating increasingly unpleasant (rotten meat) and finally dangerous consequences (or does it explode?). The questions are at once questions and answers to the initial question.

Another way to create rhythm is to use parallel structure, which means to create similar structures within a confined space. Note the similarity in the way he asks the questions: “Does it,” “does it,” “or does it.” Two of the questions also contain second parts, which Hughes structures similarly to each other: “or fester,” “or crust.”

One of the most interesting things about this poem is the way Hughes uses space. We don't usually think of poets as visual artists, but some poets do actually pay attention to the way their work looks on the page. Notice that the first line, the initial question is separated from the rest of the poem by its placement. It begins on the left margin, where no other line begins. Hughes then gives an extra line space before he begins the next section. After asking three questions, Hughes creates a new section by adding another line space. He does this because he wants the next part to be perceived differently—because unlike all the statements before and after it, it is the only line in the poem that is not a question. This is the only place where the speaker actually puts forth his own suggestion:

Maybe it just sags like a heavy load.

This gives a momentary rest from the questions that the speaker has machine-gunned at the reader. Rest and variation is an important part of rhythm. But it isn't just rest that Hughes is constructing here, he is also setting up a powerful ending. Just when we think we are done with the insistent questioning, we get another extra line space and a change in tone; suddenly the situation becomes potentially violent:

Or does it explode?

It it both part of the previously established rhythm, thanks to the repetitive “or does” and different at the same time, because it is separated spatially and tonally. The appearance of the poem on the page, which we might call "visual rhythm," reinforces the poet's theme.