I think it is important to realise when reading this story that the ordering of events, including various flashbacks, is not strictly chronological. Rather, the author has carefully chosen a series of events that shows the movement of the relationship of the two brothers from one of opposition and anger, at least on the part of the narrator, and then understanding and love. The events of the story, therefore, are carefully selected and ordered to show this gradual movement towards understanding. Note the way in which the story begins at perhaps one of the worst points in their relationship: when the narrator discovers that Sonny has been arrested for drug dealing. However, the death of the daughter of the narrator makes him think of his brother again, and whether the gap between them can be bridged. As the narrative develops, and switches between the present chronological narrative and flashbacks to their childhood, moving ever closer towards the end of this excellent story, which is when the narrator hears Sonny's music for himself, and experiences for himself how Sonny uses it to process and deal with his pain:
I seemed to hear with what burning he had made it his, and what burning we had yet to make it ours, how we could cease lamenting. Freedom lurked around us and I understood, at last, that he could help us to be free if we would listen, that he would never be free until we did.
The acceptance of Sonny and his music is symbolised when the narrator buys drinks for Sonny and his band. The story is now complete as it has arrived at the destination it has been heading towards since the beginning: acceptance and love.