For what it's worth, the Robert Johnson recordings as "traditionally" released, are not anywhere near any standard pitch--Recordings on field machines may have been of an eratic speed, but studio recordings made at the time generally were true to pitch, as evidenced by the fact that you can play along with many 78 recordings if you are properly tuned--I have tended to think that when a recording didn't match pitch, it was because the recording and playback speeds were not the same, rather than that anthing else.