I've encountered two forms of session/songswap rudeness around here. The first is in a singing session that isn't specifically a round robin, guitar players who constantly "noodle" - no-one knows if they're about to start a song, and it makes it difficult as hell for an unaccompanied singer to find his/her own pitch and melody and launch into a song.

The second happened at a local monthly shanty sing. A group of singers who were obviously good friends sat at a couple adjoining tables. Whenever someone from "their" group led a song, they were attentive and joined in. Whenever someone else led a song, they would go back to loud conversation among themselves...

I'm an unaccompanied singer mainly because I'm "instrumentally challenged" - the only instrument I've ever been able to master is my voice! However, I'm fortunate to have a partner who'll work out wonderful accompaniments to my songs on his guitar. If he's not around and I want to do a song that I think would sound good with accompaniment, I'll ask if anyone can fake their way through it in something approximating A... But if I'm singing something with George where we've worked out a specific harmony or chord, and folks around us play or sing a different chord, it really throws me.

We've been guilty of this, too. Louis Killen did a house concert here a couple years ago, and started singing a song that we had learned from Coope, Boyes and Simpson. We tried to sing our harmonies, but they didn't work. At the break, Louis said to me "Listen to how the singer is doing the song FIRST - then join in if you can do it his way..." Sound advice, whether you're talking about accompaniment or harmony or even joining in on a chorus - listen first!