I REALLY disagree with the position here attributed to Michael that sessioneers should only be playing for each other. You're betraying the tradition if you don't try to get outsiders interested in it. If you've got an audience, communicate with them."
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I agree with you Jack, performing is about communicating, if you make any kind of an arrangement with a pub you have a duty to communicate, you have entered in to some sort pf contract,
If you want to play for yourselves and you want to be exclusive rather than inclusive, do it at home.
If you wish to make rules about how the music should be learned apply it only for yourself, everyone has their own way of learning and should be encouraged in whatever way works for them.