Going back a bit on the thread, my comment re "session" v "singaround" or "singers' session" was in answer to the assertion from across the pond that "session" referred exclusively to instrumental-only events. Not so here in the UK, where there are a lot of "mixed sessions" where tunes and songs manage to co-exist peacefully, and even then, they can vary enormously in their format, from "round the room", "just jump in" or "2 songs then a tune or 2". The proportion of tunes: songs has gone up in our local session, since each person present got a turn to start something, rather than the tunesters being regarded as a single item, and no complaints about that.

But I do agree that you might want to be sure what you are going to, especially if travelling a distance, and if you don't want your session interrupted by songs, or conversely, tunes! There may be a description of what they mean by a session on a website or Facebook page, but if not, best to ask someone in the know.