How do you (politely) ask someone not to accompany you when you are preforming.
Yesterday I was playing in a session and a chap sitting behind me started playing Bodhran in a different rythym to the one I was singing and playing in. My wife leaned across to quitely ask him to desist upon which his wife picked up a very noisy shaker, the type that has circles of beads round the outside, and proceeded to accompany him, again totally out of sync with myself.
I find it difficult to play in such circumstances being distracted by the noise eminating from behind my shoulder. Not noted for my diplomatic prowess I would appreciate some help in solving this, my normal reaction would to ask them kindly to f*** **f, but as the session was run by a friend, whom I didn't want to upset this was not appropriate.

Cheers

Raggy