Grisha, I see what your'e saying now. But I'm a D/G melodeon player with no accidentals, and I don't often feel excluded when the key goes beyond the capability of my instrument. There is one particular - and lovely - tune that the locals like to play in F, and my instrument doesn't have an F natural anywhere on it, let alone a Bb (so there's not question of faking it) , but hey, I can still enjoy the tune. I have a recorder and sometimes use that for other keys, but not playing is always an option. Whatever the mental-health benefits of switching keys may be, there are definite emotional and musical benefits from just sitting and listening sometimes.

I still think that to advertise a session restricted to or including particular keys would be crazy. How would you advertise it? How would you control it? What would you do with a singer who wanted to sing in a key other than the permitted ones, or even unaccompanied? Most people would be put off attending an event where the spontaneity and inclusivity were restricted by such rules.

Marje