When Sonny and his brother look together out the window and witness the revival, Sonny says that the woman's voice reminds him of what heroin feels like:
"It makes you feel--in control. Sometimes you've got to have that feeling."
To keep from drowning in suffering, Sonny has used drugs. He explains to his brother that in order to gain anything from suffering, a person has to make it his own. For Sonny, heroin has done this, as does jazz. But, he tells his brother,
...listening to that woman sing, it struck me all of a sudden how much suffering she must have had to go through--to sing like that. It's repulsive to think you have to suffer that much."
Sonny's brother counters that there is no way not to suffer. Sonny agrees and tells his brother that there is a storm inside him that makes him feel he must play. This storm is Sonny's suffering, "Sonny's blues." His brother realizes that when Sonny plays the piano, he experiences control of his suffering:
...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 reason. And his triumph, when he triumphs, is ours.
Sonny's brother contemplates the awesomeness of the relationship between the musician and his instrument. He fills this instrument with his very "breath of life," controlling it because, as the brother realizes,
...while the tale of how we suffer, and how we are delighted, and how we may triumph is never new, it always must be heard. There isn't any other tale to tell; it's the only light we've got in all this darkness.
The tale of the darkness of suffering is the only tale because in its lighting of the darkness through his art, a man finds freedom when others listen. As Sonny's brother listens to Sonny's song of suffering, the image of "the very cup of trembling" is evoked and the brotherly relationship is deepened through the understanding of Sonny's and all men's blues.