
This is a 12-bar C blues based probably on the W. C. Handy song. The first four bars rock back and forth between the Am and E7 chords. From there it falls into a standard Gary Davis C blues. This song is a perfect platform to get comfortable playing and singing these blues.
The Rev. seemed to be able to spin endless verses from this progression. Playing blues in C with the style is a good way to break into the way he uses runs and reply to the melody and improvise. C is the perfect key for this because runs easily fall to hand.
The I is the 1st fret of the second string, The III is the open E and the V is the 3rd fret, high E. The 3rd and minor 3rd are right there: 4th fret B string to open E. The G form C chord on the 5th fret makes it easy to play the Rev.'s patented trumpet lines down to the first position.