Two adjectives that may be used to describe two conflicting feelings within the narrator when he examines his feelings about his younger brother, Sonny, are shadowed and burning [participle used as an adjective].
Like his brother, Sony has grown up in the darkness of Harlem and the "killing streets" of the housing projects. But, while the narrator has assimilated into the middle class, albeit still in the Harlem area, Sonny is yet mired in the inner city subculture. Having become a heroin addict, Sonny has lived in the shadows of alleys and tenement rooms. Even when the brother brings him to his house, he has the feeling that he has brought Sonny back to the shadows and "the danger he had almost died trying to escape."
It seems, too, that Sonny is on the edge of life, the "shadows" of experience. However, when Sonny has a burning desire to play jazz, he finds in music first "an excuse for the life he led." However, the flame of his talent carries him to a place where he can give expression to his pain. Moreover, he begins to listen to "another order, both... terrible and triumphant." This order the narrator does not understand until he accompanies Sonny one evening to a night club where he listens to his brother play the jazz and blues piano. Then, as he sits in a dark corner, where "freedom [of the spirit] lurked," the brother listens to Sonny and in "the indigo light" [burning of], his own being is stirred as he realizes Sonny is "playing for his life" with the deep and moving expressions of his soul burning through the music. As his brother listens and watches, Sonny places a drink upon the top of the piano. In his new loving understanding of Sonny, the brother observes,
For me, then, as they began to play again, it glowed and shook--"burned"--above my brother's head like the very cup of trembling.