In point of fact this notice excludes no-one – it's just an attempt to deter a few people who want to sing nothing but old familiar chorus songs, and who talk loudly while other people sing anything that doesn't interest them. (After all there is plenty of that going on only a few yards away.)

Folk music is not elitist at all but the above demonstrates that many folkies are. Or at least those responsible this notice are.

Whatever its intention may be defended as being, as I fail to see any distinction between detering and excluding, it would have excluded me, and I suspect many others who would have have thought that it was a private party. This would have been the only justification there could be for such a notice in a public house.