My group meets twice monthly as a fiddle tune jam. I wouldn't have it any other way but I've almost always got 2-5 lingerers who will hang around for a few hours after the jam just to have the chance to play some songs that sound great when accompanied by simple instrumentation -- Roseville Fair, The L&N, some Dylan stuff, some gospel stuff, Shady Grove(modal) and other old-timey stuff with words (though there is little, if any, interest in bluegrass material in my group).

My group isn't stuffy about the way the fiddle tunes are played (I have been practicing using swing chords as back-up to the fiddle tunes and, rather than being offended at the non-traditional thing I'm doing, they actually smile and seem to appreciate it)....but we wouldn't even consider mixing the jam with songs.

Even in a heavily Mennonite community (a tradition well known for choral singing) where we meet there seems to be little interest in choral singing as a social practice (like the fiddle tune jam), though our fiddle tune jam is often bustin' at the seams.