Hi Mark, We're probably talking about the same John Miller as I believe he's based in Seattle now. He recorded a couple of great LP's for Rounder in the 70's, one a collection of Gershwin tunes and songs and the other called "Safe Sweet Home" which is about my favorite guitar record. Before that he recorded for Blue Goose. Those LP's were largely country blues along with some hymns, old pop tunes, and some old time music. Oh yeah and he also played bass in Country Cooking. He's one of the few players I've heard who had mastered Blind Blakes' style and made it swing so effortlessly all the while putting his own stamp on it. More recently he recorded a fine collection of standards with the singer Rebecca Kilgore and seems to have adopted a more succinct and percussive style. The CD is called Easy to Remember and I've played it to death. Whoa, major thread creep.
One way to expand the vocal possiblities in Drop-D,besides using a capo, is to use it to play tunes in A. When going to the V chord (E) just put your thumb over the low D at the 2nd fret to get the low E bass.

Van Lingle, aka frankie