This is soooo funny, a few weeks ago at our local session, one of the participants and a very good performer got , shall we say, merry only in his case morose and then started dishing out criticism to every single one playing or singing, it was excruciatingly painful and I had to have a little word in his ear, he then went around and apologised to everyone, of course his criticisms were about spot on but hell this was a session not a performance and people go there for a night out and play and sing with friends, I once went to one of those do's where you sit around in a circle and sing, I was 19 so I suppose it was 1970 at some festival or other.....was a long time before I did that again! Not at all pleasant, informative or helpful, yes and destroying ones confidence, looking back all those years and with the wisdom of years most of it was holier than thou carping trying to establish their place in the hierarchy and feed their own egos rather than "improve" anything that I was doing. The only true advice one can give about singing a song is to find your own voice and feel what you are singing, simple (click)