Yep Shambles when talking about mostly instrumental sessions, I have found the same. I think part of the problem is that whereas most of us who go there to play together have been in the singer's position at some time or other and tend to give them the quiet we know they need (and is quite correct) but the singers have, in most cases, never been in our position and few seem to understand the session itself, the kick we get out of playing together, how the session can start to buzz, etc. I do of course know singers who may give one song during the evening but overall are there to enjoy the music and love it when a session really gets going bit they seem to be very much the exception.

Here's a summary of my overall experience (rather than saying it always works this way):

Instrumental session - most allow and even enjoy the occasional song and give the "respect" but get frustrated with long songs and with frequent interruptions. Even the purley instrumental session I go to would allow a singer to complete a song before explaining what the session was about.

Mixed sessions - A grave danger of an "us and them" situation, often with singers treating the music as background noise and then demanding silence when they want to sing.

Singing sessions - instrumentals unwelcome period.

Jon (a singer and an instrumentalist - but not much of a muscian!)