I don't remember a conductor addressing this situation because it doesn't happen often: What should you do if a string on your instrument breaks while you're playing in concert? I remember this happening to a cellist once. To my surprise, she sat down on the piano bench next to the conductor in the middle of a piece and whispered to him what had just happened.
I was playing the bass and had to turn my attention back to the music, so I'm not sure what happened next. Short of walking off stage with the cello, however, what else could she have done?
