Marje, about affordability (relative to a fully chromatic instrument with basses for all keys) I was referring to doc.tom's post of 19 May 13 - 07:49 AM. I have never had a melodeon in my arms, and the last time I witnessed such an English "session" was in a different millennium. Thus there is no problem for me personally, but I like to encourage those whose main problem is lazyness to overcome it. The benefit of playing in various keys is not only to sustain musical interest and prevent boredom: It may help keeping people's minds flexible, which many believe to delay Altzheimer's and other diseases.

The conflict (as told by the above posts, not by myself) is that choosing a rarer key may make some participants feel excluded against their will, and against the perceived character of the event.