From the performer's angle, the audience singing along as a chorus is sometimes vital, as in A Policeman's Life Is Not A Happy One. As another example, at last Monday's online Singaround, I was persuaded to do Hang Them High (which involves the end of each chorus being sung more and more discordantly); it didn't go down that well, despite Herself's help. When I'd done it at our local folk club with a live audience, well .... I've never seen an audience so entertained by bad singing.