Guess this comes down to two things for me. First, you should know the session you are playing in. The Highland Guitar group obviously has been doing it this way since its inception, so one should be prepared for that. Personally, I probably would stick to songs with predictable patterns, and I probably wouldn't frequent this type of gathering often. When I interpret a song, I rarely do it just as folks are used to. I love it when I am playing for a savvy group of folkies and they take the first verse and chorus to get to know how I arrange it, and then jump in on the chorus and sing wonderfully. But altogether too often you have the boob in the audience who refuses to go along with the way I am doing it, and insists on singing/playing "their" way.

With regard to good players jumping in and backing up the song, I don't have a problem with it. I would offer the following advice, remember to stay with your arrangement and keep it consistent in terms of pauses, measures between verses, etc. The good player won't have a problem following and enhancing your creation. Don't be afraid to let them take off on a lead break, they will be able to handle it, and if they prefer not to they will give you a sign. Again, the ones I dislike are the ones that can't "hear" the chord structure, but insist on continuing to play. I know fairly quickly if I am going to stay and play, just watch, or leave.

OH .... To Marion .... You did exactly the right thing, when you informed they in a polite way that you wanted to the song a cappella. If anyone had a problem with that, it is their problem. Don't stop. One thing about an open mic is that you want to haul out your good stuff, cause you get about one, mebbe two, songs to impress the crowd. If that is unaccompanied, so be it. Mick