Slight thread creep, but may be relevant...

A year or so ago a young duo came to play at our folk club, and the female singer was drowned out by her male accompanist constantly re-tuning during her preambles between songs. Really spoiled the performance. To me, the guitar was properly in tune, and it was merely an annoying nervous fetish...

So, as I was up to do a couple of songs after the interval, I made a point of singing a song using my standard tuning 12-string, then quickly retuning (by ear - he was using a bloody tuner!) to open D, and bashing out Joni Mitchell's 'Big Yellow Taxi', which needs a perfectly tuned instrument (especially a 12-string!), or it sounds terrible.

The look on his face was a picture, and the point was heeded!

Tunings where there are three strings all at the same pitch do tend to be more critical than standard tuning, which is why Carthy tunes more that seems necessary. That said, his new special edition Martin seems less prone to the problem than his old favourite was - though the electronics have a few bugs! I was working with him on sound last October, and it took ages to get it right, which had never been a problem with the old one! Ho hum!

I really cannot comment on JB's performance, as I've never seen her live; I've had nights when the strings worked against me, too - maybe this wasn't typical?