From an Open Culture post about Robert Johnson and Keith Richards:
Figuring out what Johnson did still consumes his biggest fans. Since his recordings were intentionally sped up, interpreters of his music must make their best guesses about his tunings.No, there’s no evidence that Robert Johnson’s recordings were intentionally speeded up. I left a comment on the Open Culture post saying just that, with links to relevant commentary by Elijah Wald and me. That was early yesterday morning. My comment hasn’t yet appeared, and I’m guessing that it won’t be appearing.
It’s crazy-making to me that what began as a “theory” about Johnson’s recordings seems to be acquiring the status of a fact. But it’s only a blue canard.
Related reading
All OCA Robert Johnson posts (Pinboard)
[I opt for speeded up. Garner’s Modern English Usage: “The best past tense and past-participial form is sped, not *speeded. It has been so since the 17th century. But there’s one exception: the phrasal verb speed up (= to accelerate) <she speeded up to 80 m.p.h.>”]