I'm reading "the Beautiful Music All Around Us" by Stephen Wade. He discusses ten field recordings from the Library of Congress collection - discussing the circumstances under which they were recorded (in the 1930's & 1940's) and discussing the singers and the communities from which they came. He writes over and over about the influences of minstrel songs, recorded songs from jukeboxes, and songs from oral tradition, and how they are mixed and reinterpreted by different singers. My guess about Brother Ephus is that there is no one definitive version and no single meaning. I wondered whether it was too religious. I like that it sounds cheerful.