This brings up an interesting situation that I am only beginning to understand. I am an intstrumentalist (fiddle), but am also a singer. Most sessions I go to are just instrumnental (Irish sessions, other fiddle sessions) or just singing (song circles). While they may tolerate an occassional mix, it is not the usual thing. I have tried with not much success to organize a mixed session. It seems that most musicians are divided into two camps - instrumental or singing and do not want to mix the two. I just enjoy the music and would like to have a mix.Regarding the problem brought up in the first post, I think it is just a matter of sensitivity and common good sense. On some songs I do not mind an instrumental back up if it is done with taste by a good musician, but other songs I prefer to do unaccompanied. Perhaps you should make that preference known before you start the song. And I agree with the advice of LTS above.
Cheers, S. in Seattle