I did see a performer in a pub many years ago just stop singing when a couple of guys started a conversation right in the front. He just looked down at them while the rest of the audience giggled.....The guilty parties finally looked up and mumbled something (maybe an apology...I couldn't hear), and the performer just said,
Oh, no...that's ok...you go and finish- I'll just start over when you're done."

They shut up, and he DID start over...