In "Sonny's Blues," the a-chronological frame of the story surrounds the flashback, which occurs in correct chronology. Therefore, the flashback represents, first, the exposition of the plot with the typical Sunday evening, which introduces the situation and perhaps also the inciting element, which might be the times the brothers hid from their suffering in movies. The flashback section also represents the rising action, which may include the memory of the narrator's conversation with the brothers' mother and Sonny's choice of jazz music over classical. The rising action builds to the climax,.
The chronology would continue with the incident that opens the story, Sonny's brother reading about Sonny's arrest, which would be a complication preceding the climax. The chronological order is then maintained in the rest of the opening frame that continues until the flashback is introduced, which, of course, interrupts the chronology. The climax occurs after the flashback. A climax in literature is the point at which the resolution is set in motion. It may also be the most emotional or emotion producing section, but emotion is not a requisite element of a climax.
In "Sonny's Blues" the climax comes when both brothers independently witness the revival and each has an epiphany, a moment of enlightenment and/or clarity, that predicts and sets up the resolution. Immediately following the revival (metaphorically and symbolically appropriate), Sonny's brother listens to Sonny's point of view for the first time and the brothers talk genuinely and sincerely about suffering and the aids to stepping out of suffering's pain. Their conversation is part of the falling action, or denouement, which leads to the resolution.
The resolution comes at the jazz club when three things occur almost simultaneously. These are that Sonny plays "Am I Blue," his brother realizes the blues have given Sonny some degree of freedom (no matter how shallow and inadequate, which is evident because he is a heroin addict and just got out of prison), and the reader witnesses the brothers both start on the path of inner freedom from suffering, although great questions still remain about Sonny's future safety and happiness.