It's not really thread drift, McG--it is an important factor when you are trying to help people deal with this situation--I don't disagree with you--I posted what I did with the awareness that Don was looking for alternative approaches--

Here is a real life folk/traditional music playing situation where this very problem came up--

A couple years back, there were a group of Ukulele players who started getting together hereabouts--the problem was that some tuned a full step above others(A instead of G), and some, the baritone uke people, tuned a fourth below one and a fifth below the other --the same E fingering on one instrument was an A on another, and a B on another.

When the Bari players (whose tuning was the same as a guitar) played a G fingering, the G tuning players had to play a D fingering, and the A players had to play...well I still haven't figured it out--if you were a good ear player, you just closed your eyes and things worked, but if you looked at the fingers and tried to interpolate, you were dead---