Comment how alliteration and rhyme contribute to the effect of the poem ''Harlem''.

This is an interesting question, since Langston Hughes's
"Harlem" is generally noted for its imagery, not its alliteration or rhyme.  The poem
does contain those things, of course, and they do matter to the
meaning.

Alliteration is all over in this work.  As the
previous post reminds us, alliteration is the repetition of initial or beginning vowel
sounds.  Take the very first lines

readability="5">

"What happens to a dream
deferred?

Does it dry
up...."

Note the repeated use
of the letter "D."  Alliteration is generally an attention-getting device which draws
the reader immediately into the piece.   It also serves to add a melodious tone to a
work, which it does here.  "Syrupy sweet," for example, is effective because it enhances
the image and even the sound of a smooth-running
syrup. 

The rhyme is fairly simple and pronounced.   The
effect of the ABAB rhyme scheme is to separate each of the images throughout the poem: 
rotten meat, sagging loads, festering sores.  One after the other, the images pile up
until the final explosion. 

The use of both alliteration
and rhyme serve to enhance the imagery of sickness and rottenness and eventual
explosion--the result of putting off (deferring) something long hoped for and longed
for.