What poetic techniques and devices does Langston Hughes use in his poem "A Dream Deferred" in order to achieve meaning and purpose?

Langston Hughes' poem "A dream deferred", also known in
some editions as "Harlem" uses imagery and rhetorical questions in order to bring about
meaning and purpose. The author is explaining what could possibly happen when the dreams
that we have for ourselves become unattainable – even the simplest dream.  He is
speaking in the context of the black community in Harlem because their situation is
often dire and it is quite difficult for them to escape their reality and achieve a
better life for themselves.  This poem depicts an unfortunate reality for many of the
poverty stricken victims who live in these types of situations.  In addition, Hughes
uses the following techniques in order to bring his purpose to
life.

He uses imagery such as: a dried up raisin that
festers, a sore, rotten meat, syrupy sweet, heavy load, explode – to project the
seriousness and the emotions that could be felt by individuals who are in these
situations.

* He also asks questions – which allow the
reader to think about the answer as opposed to him telling us what to think (effective
rhetorical device).

*He sets off certain lines to emphasize
their meaning as well - “What happens to dreams deferred?”  The author wants to show
that an issue is being raised.

* He uses italics at the end
and sets off the sentence as a possible warning.  Is this why many individuals from the
black community act out or are violent?  Are they left with a choice? Notice that the
author never tells us what to think, but helps us to think about it and to empathize
with the affected individuals.