"....someone who is obviously tone deaf'
Can honestly say that in all the time I have been involved I have never met anybody who is genuinely tone deaf - though I have often heard it given as an excuse to not make the effort.
For me, the measure of a good club is one that is capable of taking inexperienced singers and helping to develop them into good ones.
The idea that there are singers who are good enough to sing on residents nights, but not on guest nights is, as far as I'm concerned, totally hypocritical, insulting to the regulars and it certainly can't do the confidence of the less experienced singer any good.
The best workshops I have been involved with are not those guided from above by a 'teacher', but those in which the whole group takes part in the process - that way, everybody develops at each session.
Jim Carroll