What makes me completely nuts is when someone starts to accompany me on a song he's never heard before and before I can even go through the song once so he can HEAR where the tune goes, he's off and running -- generally in a direction the song never went before. I don't mean just noodling a little bit quietly to get a sense of what's going on in the song, I mean galloping off toward the horizon astride that old familair steed, the I,IV, V.Listening is good. Not every song has the same chord progression, and if you listen, you can usually tell where the deviations occur.
But ... the upside to this is that I picked up a guitar in self defense because I got so tired of trying to communicate a song to someone. I haven't tried to jam now that I can actually play guitar a little, but I figure if they still won't listen, I have a large, blunt object with which to whap 'em upside the head. ...
By the way, marion, I sing unaccompanied a lot, too, and I am utterly unabashed now at saying, "I sing this unaccompanied." Thanking them for playing is a gracious thing to do though ... it's good you're being that thoughtful, and that ought to put you in good stead when you go back.
ww