Without going into a lot of detail, check out Josh White, who played with Leadbelly as well as with a number of blind bluesmen in the 20's, 30's and 40's. There is a lot of information on him and on the peripatetic lives of these blind singers on Google. He was one of my earliest influences. In his prime, there was probably no more powerful and influential performer, whether in blues, gospel or even Tin Pan Alley" genres. He crossed racial lines, performing in clubs and theaters formerly "white only." He was also a vocal and visceral champion of racial justice. Listen to "Strange Fruit." He ran afoul of the "red-baiting" tactics of Senator Joe McCarthy, though basically apolitical, and was blacklisted for much of his later career. Some criticized him for being "too polished." But his playing influenced numerous others, including Dylan. Listen, if you can find a recording, to his fingernail work on an old Martin (00-18?). No picks.