I always admired the late Iain McKintosh - not just for his singing and musicianship but for his ability to handle an unruly audience. Normally this was done by playing and singing ever quiter until the offender stopped by themselves or was "SHHHUUUSSSHED" into silence by the rest.
He did however tell the story against himself about the very vocal young lady who just would not shut up until he finally made some appropriate comment about her. During the interval he made a point of seeking her out and apologising for embarrassing her when he was on the stage. "Oh," she retorted, "Were you on the stage?"!

Eddie