I propose we move past the Crossroads bit - the OP isn’t asking about that and RJ can and should be respected for his contribution to the blues and, ultimately, rock much more than a bit of story that took a long route to get to RJ apparently…
Crafter Man by looking at the video clips like Grossman, do you get a sense for how to play fingerstyle blues?
I think that Grossman video shows best how they do it. Look especially at the part where he says he plays it like they did in the '30s. You can easily see the bass strings vibrate as he plays the higher strings.
Or you can do it like Mike Rayburn:
I think it is safe to say that nobody actually sold their soul to the devil and that such a story is a marketing ploy. If I am mistaken, then the blues club in hell must be especially awesome.
Probably not. If B.L. Zebub gave them their talent, hell for them is probably having it taken away. Whole stage full of inept plonkers and wailers. shiver
Go to the fork in the road instead of all the way to the crossroads.
Yea, that’s what I’m talking about. Grossman is really good, especially there at the end of the video. But I must say, Robert Johnson’s playing on the CD is quite a bit more intricate and faster than even Grossman. Johnson just sounds so damn… confident. Wish there was a video of him doing it. 
Some say the recordings are up to 20% faster than his actual playing.
He also uses alternate tunings in some songs which make things easier to play (relatively speaking).
I don’t do it much any more, but I spent about fifteen years remastering 78s from my personal collection. This included speed correction, which has to be done for most records made during the 78 era. I feel confident in saying that a 20% speed correction is ridiculous, especially for records made during the thirties. 20% is almost four semitones. Some records made during the thirties were off by as much as 4%, but I’ve never seen one coming anywhere close to 20%.
So, you’re implying the Blues Club in Hell has probably got better music than Rock and Roll Heaven?
Oh no. Jerry Garcia is in heaven because God is a Deadhead.
How could you tell what the original speed was to do your speed correction?
For Robert Johnson, a few years ago someone (on a different message board, I think) suggested looking for the 60 Hz electric line frequency. I did that, and there was a single frequency in every song I checked, at 51.4 Hz. Back then, the electric line frequency hadn’t standardized on 60 Hz yet, and at least some power was at 50 Hz, but I couldn’t find out for Texas where he recorded.
If that is 50 Hz line frequency, then his recordings are fast by 2.8%, or 1/4 step, in line with what you typically found.
(Or maybe it was 60 Hz, and his music was slowed down 15 percent, and Robert Johnson had a chipmonky voice. But boy could he play! :))
… and when you’re done with people like Robert Johnson start having a look at someone like Tommy Emmanuel or (even better) Leo Kottke. Particularly the latter makes it sound like Robert Johnson isn’t doing much.
By the thirties the nominal speed for almost all records was 78.26 RPM, but many were actually recorded at different speeds. The standard practice in remastering is to play the record back at a known speed (usually 78.26) as a starting point, and either speed it up or slow it down so that the recording in on-pitch.
It helps to know what key the piece was written in, or lacking that, what keys were likely to be used given the instruments involved. Even more important than that is the knowledge of what the instruments and the human voice naturally sound like.
The presence of voice makes it much easier, and fortunately we have that with Robert Johnson. A voice that’s played back too slowly will sound sluggish - the vowels will be drawn out unnaturally. Any vibrato will be too slow. The attacks on plosive consonants will be too long. The transitions between notes will be too drawn-out. It doesn’t sound like someone singing slowly - it sounds “off.”
You can also get some clues from the sounds of the instruments. Guitar, for example, has a fairly sharp attack. When played back too slowly, the attack will be drawn out and sound unnatural.
Some of those who claim that Johnson’s records were recorded 20% slow say it was done to fit Johnson’s songs on a single side because they tended to run long. This is not how things were done. They would control the groove pitch - the amount the stylus would move toward the center on each rotation. For longer-running records, they would set the groove pitch low in order to fit in more rotations (and thus more time).
For example, the article linked to above refers to Come on in My Kitchen. I looked it up on Youtube - here it is played at normal speed, and here it is slowed down by about 20%. The playing time of the former is 2:51, and the latter is 3:39. It was possible to fit three and a half minutes onto one side of a 78 in those days. It wasn’t common, but it could be done. The lack of deep bass on a recording like this makes it easier because the groove oscillations wouldn’t be very large.
In addition, the record companies wouldn’t have made special adjustments for someone as obscure as Robert Johnson when he was alive. Johnson is famous now, but at the time he wasn’t well-known and the record companies wouldn’t have expected to make a lot of money off of him. They would have put him in front of a microphone and told him to play.
As for tuning to the hum in the recording - this can work very well if the recording has hum. Many of them didn’t.
How do you know what “on-pitch” is? Are you just assuming A440? That wasn’t standardized until 1939.
So this thread has careened from soul-selling myths to official recording speeds and pitch standards.
My brain hurts. The OP was looking for technique.
But - just to perpetuate the madness, I give you this: Robert Johnson Photograph - The Unofficial Martin Guitar Forum
A kerfuffle thread from the Vintage Corner forum about a photo asserted to be the 3rd known photo of Robert Johnson. Acquired on eBay by Zeke of Matt Umanov’s shop (I know him - nice guy and great player), and written up in Vanity Fair magazine…
Somethin’ about Mr. Johnson just elicits kerfuffles, apparently…
Even before 1939 most American musicians were tuning somewhere close to 440. So yes, I assume A440, and if I’m off a little bit, so be it.
My original point was that Robert Johnson’s records weren’t recorded 20% slow. I didn’t mean to derail the thread - I was just trying to justify my position, which is that Robert Johnson’s records sound the way they do not because they were speeded up, but because he was a really good guitarist.
Unless Robert Johnson carried a tuning fork with him (which seems unlikely), his only concern would have been that his guitar was in tune with itself (and with any other instruments if he happened to be performing with additional musicians).
Concert pitch would have been irrelevant, and, absent a tuning fork, unattainable.
I can certainly agree with that, regardless of how he acquired his skills or what pitch he tuned to 
