I have got to reconnect my turntable--as all of my Reverend Gary Davis stuff is on vinyl and now I've got a jones to hear that song--and you are a lucky so and so to have gotten to hear him in person--As to speculation and the blues, part of the appeal, to me, anyway, is just that--no one really quite knows where it came from--it sort of appeared--
Handy wrote that he first heard the blues from a street musician on the railway platform near where "the Southern Meets the Dog" and In my more reflective moments, I can see myself on that lonely platform, surrounded by the flat, dusty fields, and then hearing, for the first time, a bottleneck slide across the strings, while a voice moans, "I hates to see that evening sun go down....Oh, Lord!!!"
Ma Rainey had the same kind of story--and so it must have been--the blues was just there--and one day someone just noticed it--