Sweet Blues! Coming from a black man's soul (14-15)
Like in line 3, the speaker is pointing out the importance in the singer's race. If the speaker is a black man, this is an occasion for racial pride and self-confidence.
"Ain't got nobody but ma self" (20)
The speaker identifies with the musician, but it's never clear if the musician identifies with his audience. We really only have the song lyrics to rely on. The lyrics suggest that the musician is singing the blues for himself. Maybe because his performance is a form of therapy for him, and the performance is just how it comes out.