Dick wrote:-
"very good post, vic, how would you have dealt with that situation?"
Well, if it had happened in my club, here's what I ought to have done.
1] Gone after the young couple, apologised on behalf of the club, told them that such an occurrence was highly unusual, that the singer was out of order and that I hoped that they would come and try us out on another evening. If they did come again, make sure that they had a friendly greeting from me.
2] Speak to the singer on his own, tell him that anything to to with the conduct of the audience (or performers) that needed addressing was a matter for someone from the club organisation and not for him.

However, I have had time to think about it. Whether I would have been quick-witted enough to do it as the time, I don't know. We can all be wise with hindsight.

Craigie Hill wrote:-
"One suggested I was pitching too high & missing top notes as a result, the other said I was wavering around the tune at the start."

a) Pitching - ask yourself if the comment was valid. I know that I have been cross with myself for pitching things too high on occasion and I do hear it from others though I would not comment unless I was asked.
There is a double album by one of my favorite Scots traditional singers. I admire this man's singing great, but there are probably around 6 tracks where he has pitched the song too high and his great voice sounds strained on the top notes - and this is on CDs so it is there for all time. I wish I had been in the studio when it was recorded; I know him well enough to have said, "Listen to the playback of that track. Have you pitched it too high? Do you think that you should record that one again? If it is an accompanied song that you have been singing for years, you have to be aware that with age, your singing range will diminish, particularly with age and that you may need to put songs in a lower pitch.

b) wavering around the tune at the start - This is very common, particularly when people are singing unaccompanied. Finding the tune by the end of the second line, say, is a characteristic of many field recordings. I am so used to hearing it that I scarcely notice it any more and am tempted to say that it does not matter that much.

The great Isabel Sutherland - whom I greatly admired and learned a lot from - used to introduce her songs and then close her eyes for about 3 or 4 seconds then open them and start singing. I asked her why she always did that. She said that she was finding the exact spot in her head where the right pitch, the tune and the opening lines of the song were located. I have tried that and found that it works.
If you are singing to an accompaniment then the instrumental accompaniment can serve this purpose.