There are some very thoughtful answers in this thread. In particular, I agree that Hughes's singer is in fact speaking for the entire African-American community. I think he has poured everything into his performance, and now he's sleeping soundly, having given all he has to give that night. It also speaks to the authenticity of the singer, as he finishes the song with the line "and I wish that I had died." He goes home, with the blues still in his head, and indeed sleeps like the dead.

All the previous answers are valuable, but I was especially intrigued by the third, which gave me a perspective on the poem I hadn't considered before. I had always assumed that the speaker sleeps as if he is dead because he is so depressed, and that sleep is a kind of relief from consciousness.  The idea that he sleeps because he is at peace and is satisfied is one I hadn't considered before.

I think the last line is actually a reflection of the massive troubles that faced Afro-Americans at the time of writing the poem. The sufferings of discrimination and racism meant that death in these last lines is a sought after escape that will end those sufferings and tribulations and give freedom in a world where freedom is absent. The other posters are correct in identifying that this last line relates to the mood and tone of this poem, but let us also remember that Hughes wrote political poetry. He is not really saying that death is something to be wished for, but rather is pointing out that death could be viewed as a welcome release from such suffering.

As the previous poster stated, the word "dead," in part, completes the rhyme as it rhymes with "head." Beyond that, I think the use of the word completes the mournful mood of the poem. Though I do not think it suggests that the man is actually dead, it gives that note of finality. It brings the poem full circle and highlights the heaviness of the scene.

This man is mourning his life and the fact that he has such a heavy, or "dead" sleep could suggest that singing the blues has given him the "satisfaction" he says he does not have. He is able to "sing the weary blues," and then fall asleep. Perhaps he is able to sleep well as a result of singing the blues.

I'd be interested in seeing this moved to the Literature Discussion Forum so we could all share impressions and interpretations.

I choose to view the use of the word "dead" as being primarily dictated by the need to maintain the rhyme and meter through the last three lines of the poem. The musical quality of the entire poem is reflected in the care given to the sound of the words and the way in which they are put together. The meter is based on ten syllables in each of those lines, and the rhyme carries through all three.

Certainly, there is the possibility that the singer's wish came true. The blues had become overwhelming and he saw no hope for any future improvement of his lot in life. It is very possible that when "the stars went out and so did the moon," the singer's light was also extinguished.