To be honest all the sessions I've ever been to A is an accepted additional key anyway and I wouldn't sit long in a good session without somebody going off into A. I can play in A on the DG melodeon, stuff like Athole Highlanders, and on my concertina I have ADGC anyway so Bluebell Polka isn't a problem. If I was in a session and enough non-restricted instruments were there as well I'd probably give it the full works, but if it was mostly DG boxes I'd miss out the C. Banjo players frequently shoot off into A and you either follow or have a sip of your pint. If somebody starts up in some exotic key, it's obviously someone after a solo so you sit politely and listen.

I understand your point, Will, but for me the main point of a session is as many people joining in as can and having a good old time.