McTell’s earliest recordings were cut in Atlanta, New York City, Chicago and Augusta, Ga., for a number of labels, beginning with Victor, from 1927 to 1936. Next comes a single-day song-and-talk session for the Library of Congress, recorded by John Lomax in 1940. The third period, 1949- 1950, includes sessions for Atlantic and Regal. The last is another one-day session of songs mixed with conversations in Edward Rhodes’ Atlanta record shop in 1956.

When Sam Charters released those final sessions in the fall of 1961 as Blind Willie McTell: Last Session, McTell’s music became part of the canon of the folk-blues revival. In 1965 Taj Mahal recorded McTell’s “Statesboro Blues.” Duane Allman heard it and turned it into a guitar fury, playing it regularly at the Fillmore East in March of 1971 with the Allman Brothers. In Allman’s hands, “Statesboro Blues” became a classic.

Later, Bob Dylan released a song called “Blind Willie McTell” with the refrain, “And I know no one can sing the blues/Like Blind Willie McTell.” More recently, the White Stripes’ Jack White performed in the bluesman’s home state and announced to the unwitting audience that he was proud to play McTell’s birthplace. If one listens the right way to the White Stripes, one hears McTell riffs unleashed with an inverted ferocity.

The book is ultimately about America, too, as it examines everything from a vision that seeks to perceive how the music that changed the world forever was made against all odds. McTell plays 12-string like a piano gone mad. He sings like a man possessed with vision. He never knew it, but he made recordings that forever altered vernacular music patterns and he did so in an offhand, casual manner, even if there was a microphone shoved at him between street corner gigs.

Gray is as insightful as anyone could possibly be on all fronts, safely leading McTell from gig to gig, titling his book from a line in “Statesboro Blues” that defines McTell’s wandering way of life and composition method.