Ron olesko.there is plenty of evidence of sloppy performances outside of folk clubs.,vis my examples of the Stones and the Beatles in hamburg, Plus yank rachels mandolin on a Sleepy john estes recording.
I also have a recording of Sonny Terry and Brownie MCGHEE, at the end of one track Brownie quite clearly, says try playing in A sometime., [sounded like SONNY WAS PLAYING IN THE WRONG KEY].