The climax of "Sonny's Blues" occurs after Sonny returns to Harlem to live in Greenwich Village, and they have a heated argument.
James Baldwin, who composed songs at one time for Ray Charles and was close friends with trumpeter Miles Davis and others, gives to his "Sonny's Blues" much musicality. Because this story is much like a blues song that has a recurring melody, the progression of the plot often returns to a motif that is repeated throughout the narrative. It is in one of these recurring motifs that the climax occurs.
The middle of the story is composed of the narrator's recounting of his past experiences with Sonny. They argued continually, and the narrator realizes that while he is at the piano, "Sonny was...playing for his life" because he was wrapped up in "some vision of his own." But, the music bothers the narrator's wife Isabel and her old father, so Sonny stops playing until he feels he must leave.
Climax (in the past):
After having both been in the service, the brothers return to Harlem, and they have a serious argument and Sonny again leaves. The brother finds him living in Greenwich Village and tries to ameliorate things; however, Sonny acts as though his friends there are of more significance than his brother, so the narrator starts to leave. Sonny tells the brother to just consider him as dead; the brother hears the door slam behind him and the friends laughing. But as he walks away he whistles to himself the lyrics, "You going to need me, baby, one of these cold, rainy days."
Back to the present:
Then, after Sonny gets out of jail and stays with his brother, the narrator observes Sonny across the street from his house, listening to some street preachers singing. The narrator observes of the Harlem listeners,
...the music seemed to soothe a poison out of them; and time seemed, nearly, to fall away from the sullen, belligerent, battered faces, as though they were fleeing back to their first condition, while dreaming of their last.
Then he sees Sonny, "standing on the edge of the crowd." This moment is truly symbolic of what later occurs. For, after Sonny comes into the house, he and his brother talk about the revival across the street. It is then that Sonny asks his brother, "You want to come some place with me tonight?...I'm going to sit in with some fellows in a joint in the Village."
The narrator agrees to do so, and the brothers talk about music and life. Sonny explains that for many who suffer, drugs have "made something real" for them, especially if they play music.
"There's no way not to suffer. But you try all kinds of ways to keep from drowning in it, to keep on top of it, and make it seem--well, like you."
The brother/narrator accompanies Sonny to Greenwich Village and sits in a dark corner of a nightclub waiting for Sonny to play. A big man called Creole greets Sonny and invites them into "his kingdom." As Creole and the others begin to play and the brother watches, he realizes that listeners hear their own personal evocations, but those who play, those who create the music
...hear something else, ...dealing with the roar rising from the void and imposing order on it as it hit 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. And his triumph, when he triumphs, is ours.
The brother watches Sonny's face. He realizes the challenge of man and instrument; for, he must fill it with the breath of his own life, and make it do what he wants it to do. Watching Sonny, the brother witnesses something hidden "being burned in it," and the piano then tells the tale of Sonny's suffering.
I seemed to hear with what burning he had made it his, with what burning we had yet to make it ours, how we could cease lamenting.
The music, that song of the soul, becomes solace for suffering of both brothers as one plays and the other listens. After a girl brings Sonny a Scotch and milk on top of his piano, Sonny sips from it--the very "cup of trembling" from Isiah 5:17-22 [Baldwin was a preacher's son]--and the brother grasps the symbolism of the cup and is finally in communion with his blood brother.