Have to agree with synbyn that it's all down to the organiser, who must strive for high standards. Try Stony Stratford for some fantastic sessions which have great variety of music and song, lovely whistle and fiddle music, always great singing, very folky and often traditional, but never other forms of music. It's how a club is. If it lets things slip, then people do take advantage, but if the organiser is sensible, then people know what the club is about. Folk music is very precious and is different to other forms and we need to preserve it, sing it, play it and enjoy it.