When I saw Gordon Bok last year, he kept forgetting lyrics. I don't think I've ever heard a performer blow more songs. He apologized, and said that he sings bass when he sings with Muir and Trickett, and he's gotten lazy since he can fake it and let them fill in when he forgets lyrics. I'm not very good at remembering lyrics myself, so I often make up lyrics on the fly while I'm singing - with varying amounts of success. Despite his forgetting lyrics, it was a wonderful concert. His memory lapses added a very human touch to his performance.
Bok, Muir, and Trickett don't hesitate to change archaic lyrics to make them understandable to a modern audience. I suppose some people don't like that, but I think they do a good job of it.
-Joe Offer-