He recorded on Dictaphone wax cylinders on a portable recorder - pretty crappy even by 1928 standards I would guess.

I don't think it has been digitised - the cylinders were recorded onto tape (reel to reel?) in the early 70s, and the tape burned onto CDRs recently.

Most of the recordings also have a corresponding text and/or music notation. The originals are in the Libary of Congress and a microfilm copy in England at Cecil Sharp House. Anyone fancy going there and copying 400/500 song texts?