The dialogue and actions of the characters provide a chaotic vision of a desperate society, deeply ailing on every level. Each member of society seems to be breaking under the strain, and additionally brittle from the long days of too much heat and no rain. By contrast, the tone of the narrator is carefully measured, and highly controlled. The scene just before Will is abducted from the ice plant is a good example:
He [McLendon] struck the Negro. The others expelled their breath in a dry hissing and struck him with random blows and he whirled and cursed them, and swept his manacles across their faces and slashed the barber upon the mouth and the barber struck him also. (3.20)
The actual scene is one of chaos, a scene of one against many, of blows and curses and confusion. Yet, the narrative voice keeps its head, calmly, though energetically, letting us feel the chaotic action. Through the tone, we come to understand that this is a sad moment in the story, for all the obvious reasons, but also because it's the moment where Hawkshaw and Will come to blows against their wills. In general, the tone of controlled chaos helps us foster and maintain a sense of calm needed to properly analyze the chaotic events of the story.