I think that Hughes employs a variety of images in the poem to show the complex nature of freedom.  The piano player, in his own right, is shown to have freedom.  Yet, this freedom is not entirely liberating, not entirely clear in terms of its absolute nature of redemption.  Instead, "the weary blues" is the freedom of the piano player.  Hughes constructs freedom as something where results are uncertain.  The piano player has the ability or the freedom to play his music, "the weary blues."  Yet, the images he presents of this freedom are ones that show freedom's complexity and its ambiguity.  For example, the "lazy sway" and the "croon" are all a part of this freedom, aspects that show how freedom is not absolute, but rather something that can involve elements of pain and suffering. The "moan" of the piano as well as the fact that the piano player "got nobody in all this world," are images of freedom that reflects how there is a pain and hurt intrinsic to the process of liberty and self definition.  These images bring out the suffering that is a part of freedom, revealing its complex and intricate nature.  When the close of the poem shows freedom as "the weary blues" echoing in the piano player's head, it shows freedom to be something that does not contain liberation, but rather reflects hurt and pain.  This is something that Hughes uses to construct his notion of freedom, complete with images that bring out how "the weary blues," or the expression of freedom does not always contain elements of happiness.  Rather, freedom is seen as complex, complete with complex images in Hughes' poem.