Hey John J...no offense but it seems like the problem is that you want everyone to sit quietly and pay attention to you performing by your self. I guess this is fine for some sort of pre-arranged song club event, but if this is a session then let him play...or stop performing songs that you don't want anybody to play along on. The other alternative is to sing the song in your car on the way over, and get it out of the way before you show up to a social event. The only other thing I can think of is to get yourself a gig somewhere by yourself where you don't need to be annoyed by other people who also wish to play and can still have everybody pay attention to you.