There is power in music. The narrator in this story, a young man who has searched out and found a renowned blues singer in Louisiana, ponders what this singer means, what has inspired her to sing the way she does, with the pain that she does. It's a touching scene at the end when the young man finally gets the chance to listen to Mayme perform. He is struck by the emotion in her, by the emotion her voice evokes in him.
"Fallen angels could never have wailed like this, no matter how they grieved over parardise."
It's a rather perfect description of the effect of listening to music, particularly blues music. Bontemps is obviously a fan. Now I am one of his writing and I'm glad I stumbled onto him.