Christopher Guest has been brilliant for longer than I've been alive. Of late he's been doing his mockumentaries and doing them well. He'll always be immortal for This Is Spinal Tap. Even in the '70s, when nobody knew his name, there wasn't any stopping him.
These clips come from the off-Broadway National Lampoon stage show "Lemmings," where a heavily bearded John Belushi and a long-haired Chevy Chase performed live from New York two years before Saturday Night Live. Here, Guest does (and does in) Bob Dylan and James Taylor.
Trivia time: When Chevy was at his old school, he drummed with Walter Becker and Donald Fagen, who went on to be Steely Dan.