My father, who died a few years back at 73, was an afficionado of old folk tunes, particularly dealing with war, as a professional soldier and a guitar player from Middle Tennessee.
About everything he knew, I believe he got from an old black gentleman who had not traveled much, but got his tunes from get country togethers. This was the man who taught my Dad to pick.
Every verse he ever sang of Soldier's Joy -- a favorite of my brothers and me, related to the Revolutionary War (and there were far more than I have seen anywhere on the internet). I remember there always being a serious drop at the chorus, which we never thought the old man cuold make, but he got down there. My Dad's voice was low. I think he played the tune in C or something.