Hello, is anyone listening?

I'm all for instrumentalists joining in with songs (but not if they force a change of key - I did see that happen at Tenterden too - some of you know who the guilty fiddler was). It's generally a bit tricky on songs when the singer does not play, because then (s)he is often not in concert, and usually wanders a bit, as the song goes on.   If the song has rhythm (some don't) the otherwise solo singer is usually best (very carefully, watch like a hawk) accompanied with drum (insert type of choice).

If the singer plays and is accompanying self, I see no objection to instrumental accompaniment, and personally welcome it if I am the singer - so long as the accompanist listens and follows.

I have also had some wonderful serendipitious accompaniments when I was singing without my guitar. I remember one time Royston and I were doing a shanty (Haul away for Rosie) and we had asked for a B to start us off, and about halfway through the first chorussy bit a guitar was cooking up a real storm (a bit blues-y but none the worse for that) behind us. I looked round, guitarist stopped, and I had to tell him (hand gestures while singing, tricky to convey absolute meaning) to come back in. It was great!

But it is not great to be asked to sing/play in G or D if the song is not good for me in G or D.

If you get players going "this is too easy" I find that "Henry Martin" often sorts them out.