So you're watching some wonderful solo guy who you've loved for a while. He's playing some of his new stuff which is alright, but not half as good as the records that made him in his heyday.
Then he plays the opening chords to that fabulous song everyone loves by him from his early days.
But then he goes and RUINS IT by changing the entire phrasing of the vocal line - meaning not only can you not sing to it, you can't enjoy it very much either.
Y'know what I mean?