or a bit More Revisionist Music History...
I know the internet is full of rubbish and this might well be another bit, but I've just been reading Steady Rolling Man which looks at Robert Johnsons recordings and asks whether the bluesman we know may well be the product of archaic recording techniques. It's proposed that RJ was recorded at the wrong speed and pitch and there some examples of his recording slowed down and reduced in pitch. I've had a bash at lowering the pitch on these samples. I'm not completely convinced but I think there may be something in it. I always thought that the original Dock Boggs recordings have a similar feel.
Crossroad Blues original
Crossroad Blues pitch lowered 10%