Brian Peters wrote
"Mind you' I've heard the great cajun player Steve Riley execute key changes in mid-song that really ought to be technically impossible on a ten-button one row!"

Yes, I've heard him do it at the Festival Acadian in Lafayette, but in spite of the exhilarating brilliance of Riley, Savoy, The Balfas etc, of that weekend, it was noticeable that the vast majority of the music throughout the festival was played in G.

Mark Savoy's website says that he will make accordions "in any key" but I'll bet the majority he makes are in G.