Was watching Christopher Guest on Charlie Rose last night. VERY interesting. Had gone to a free showing last week of the show, and enjoyed it immensely. My friend, who IS one of those folkies from the 60s/70s, said she was going to run out of the theatre,if she saw herself in any of the characters. She did, but stayed to watch the whole thing. Laughing all the way.

Mr Guest said that he doesn't really "script" most of his movies. . He sets up a scene, with characters in place, tells the characters what the scene is to accomplish, and let them go at it. Before the movie even begins, he and the other writers, (in this case Eugene Levy), would come up with the basic scenes, and a thorough back-story for each character and how they interact with each other. All of the dialogue is generated on the fly, for freshness, right on the spot.

Apparently, the singing on stage was all done live, and by the actors themselves.