I was thinking of a few examples I have had, but on reflection, most were heckling which is a different thing entirely...

I used to be interrupted when practicing in an earlier life, but to be fair, wedded bliss now includes not being interrupted.

During a singaround, you can end up competing with other conversations in the room and it isn't unknown for someone to drag me into their conversation when I am in full flight. Mind you, I am thinking of one particular old bugger....