How did the author create the tone in Sonny's Blues?

James Baldwin effectively creates a blues/mournful tone in his story of "Sonny's Blues" by having the disappointed brother read about Sonny in the paper "trapped in the darkness which roared outside."  He narrates that a "great block of ice got settled in [his] stomach as he read about Sonny's

trouble in the spring.  Little Grace died in the fall...she only lived a little over two years.  She died of polio and she suffered.

Then, like in a blues song, memory crashes in upon the narrator as he see a "boy standing in the shadow of a doorway, looking just like Sonny...a boy from around the block" who has come to talk with him about Sonny.  His tale is morose as he says he feels responsible for Sonny's misfortune.

After an awkward conversation with this person, the narrator recalls a letter from Sonny in which he tells his brother how much he needed to hear from him.  This sadness of distance between the brothers continues as the narrator writes of Lenox Avenue in Harlem as "a hidden menace which was its very breath of life."

Into this dark area Sonny returns.  But, while the nephews remember him, the narrator remains full of "that icy dread."  Memories of his dead father emerge along with the "darkness" until the mood is broken as Sonny returns home and he and his brother talk.  Sonny invites his brother to the jazz club where he is to play that evening.  In the dark corner where he sits emerges the moral truth to the narrator:  Sonny is a sensitive man who needs the ear of his brother; he needs the love of his relatives; he needs them to listen when he plays the blues.  As the narrator explains this moral truth:

And even then, on the rare occasions when something opens within, and the music enters, what we mainly hear, or hear corroborated, are person, private, vanishing evocations.  But the man who creates the music is hearing something else, is dealing with the roar rising from the void and imposing order on it as it hits the air.  What is evoked in him, then, is of another order, more terrible because it has no words, and triumphant, too, for that same reason.