John Kenneth Muir's book, Best in Show: The Films of Christopher Guest and Company, reflects on the making of those two movies, plus A Mighty Wind. The book was published in 2004, before the release of For Your Consideration.
Guest doesn't like the term "mockumentary" to describe his films because he thinks that suggests he uses the films to mock dogs shows, folk singers and small-town people with aspirations for Broadway. He prefers calling them comedies done "in a documentary style." Muir uses "mockumentary" anyway, and I think he is justified in doing so. First, the word has become widely used in reference to Guest's comedies. Second, the term means not just belittling or making fun of something, but also imitating something, such as a mock battle or mock turtle soup. Guest's movies play like true documentaries, but with that one step further that makes them great comedies.
Guest's screenplays are much shorter than the screenplays for most movies simply because he omits all dialogue. He chooses actors such as Catherine O'Hara, Eugene Levy, Michael McKean, Parker Posey, Jane Lynch and Fred Willard who have great improvisational skills. Then Guest just sets the scene, starts the cameras rolling and lets the actors make it up as they go along. Most of this footage never sees the screen. The editing process can take more than a year. In the case of Best in Show, 60 hours of film was trimmed into an 84-minute movie. For A Mighty Wind, Guest cut 80 hours down to 90 minutes. Sometimes the funniest scenes don't make the final cut simply because Guest decides they are not necessary to tell his story.
I read this book over several days, and in the evenings I watched yet again the three Guest films Muir writes about. I have always liked Best in Show best because it is the funniest, and I liked it best again this time. Yet Muir makes a good case that A Mighty Wind may actually be the best movie, "the apex of the director's career." It may not be the funniest, but it has more heart and it ultimately tells the best story.