"The performer can and should invite participation or indicate not"
Circular argument Virginia; If a singer makes such a request for an audience not to join in, Richard, and those who think like him will be there to tell he or she that they consider themselves better than the rest of us. Where do you go from here? Surely the practice should be 'only join in when you are invited to do so'.
For the record (and off topic) I have never advocated that the introduction of non folk songs muddy the water - only that what goes on in folk song clubs should fall within recognisable parameters of the definition - ie they should sound like folk songs. Does the rendition of a pop song draw in youngsters? Most youngsters I know are fairly discriminating as to the quality of the music and virtually all the pop songs I have heard done at folk clubs have been executed fairly diabolically.
Jim (I prefer Jim - Mr Carroll makes me sound like my father) Carroll