I recall being in a pub one Lancaster maritime festival, where Paul Sirman attempted to sing a well-known song to a slightly different arrangement and chorus. However, lining the wall behind him were the members of three well-known shanty choruses/singing groups, including the Keelers and Th'Antiques, and he was soon shown the error of his ways when they kicked in with the proper chorus! Poor lad, he took it quite well. Not that he had a lot of choice!

I'm not quite sure of the morality of this story (other than know when you're beaten and smile), but it does seem to fit the theme of this thread.