Folks, I just ran across this old photo, and thought you’d like to see it. This was take in Florida on a warm day in August 1969 (every day on August is warm in Florida!), and it shows banjo wizards John Hedgecoth and Mike Johnson showing off by playing each other's banjos-- Mike was doing the right-hand on his banjo and the left hand on John's, and John was playing the right hand on his own banjo and the left hand on Mike's!
(Click on the photo for a larger version. Mike’s playing his old Gibson bow-tie RB250, and John’s playing his then-new RB800.)
The tune they were playing was "Cripple Creek." Mike and John could play it this way because they'd both learned it right (read: they’d learned Earl Scruggs' version). This meant that they both knew exactly which left-notes to finger on each other's banjos all through the tune, and they both played exactly the same rolls with their right hands, and it all worked and sounded great!
However, at the moment of the photo, right in the middle of the tune, John had detected that his second string was a bit flat. So, timing it just right (during the square rolls in the B part, so Mike's notes would blend with his), he deftly reached over to his own banjo's tuners and adjusted that B-string note, then went right back to playing those Cripple Creek licks on the fingerboard of Mike's banjo. Nobody noticed. Unless, like me, they were right there watching. Or unless they saw the photo!
The moral is: Some pickers can tune a string in a short time. Also, don't forget to practice Cripple Creek! --- Just in case you ever get a chance to play two banjos at once...