Improvisation is frightening.

I speak from the experience that comes withthree years of advanced drama and a dozen harrowing brushes withimprov. If performed in the wrong hands (sometimes mine),improvisational performances can be excruciatingly painful.

When accomplished successfully, such as inChristopher Guest’s “A Mighty Wind,” the performance can bemesmerizing. He has accomplished such a feat three times. In 1996,he presented “Waiting for Guffman,” a look into small-towncommunity theater. Four years later, he directed “Best in Show,”which explored the politics and fanaticism behind dog shows.

With “Wind,” he has delved into the world offolk music. For each film, Guest has written a detailed outlinewith Eugene Levy (who has also appeared in all three films withGuest), and left the fleshing out of characters to his criticallyacclaimed cast. He edits each film extensively from about 100 hoursof footage, eventually creating 90-minute masterpieces thatpractically scream “genius.”

In the film, folk music pioneer IrvingSteinbloom dies, and his children plan a reunion concert with threeof Steinbloom’s most beloved acts.

The Folksmen (played by “Spinal Tap’s” Guest,Michael McKean and Harry Shearer) were one-hit wonders whoserecords would have been timeless classics if only their producershad put holes in the center of the albums.

The New Main Street Singers are a newgeneration of a classic folk group, with Jane Lynch, Parker Poseyand John Michael Higgins as the main members. Lynch and Higgins’married couple have a few bright spots in the film as the faithfulfollowers of a colorful religion that Lynch’s character created andembraced with a frightening intensity.

The third group, the romantic duo Mitch andMickey (Levy and Catherine O’Hara), have been estranged sinceMitch’s 1970s meltdown, the aftermath of which is portrayedwonderfully by Levy, who is clearly going for a Jerry Garciaapproach to Mitch’s mental problems.

Fred Willard, Larry Miller and JenniferCoolidge round out the main cast as the manager of the New MainStreet Singers and the PR agents for the reunion concert,respectively.

There are a couple of factors thatmake the film so great. First, there’s the writing and directing.While there was no prepared dialogue when filming began, Levy andGuest’s outline and story idea are the driving force behind themovie. Their talent as entertainers and writers can be proved bythe fact that they can take subjects that virtually no one caresabout, and make them undeniably fascinating. Their characters areembarrassingly clueless, with earnest, completely seriousattitudes, which only makes the documentary-style of the films morerealistic.

Second and most important, the performancesmake “A Mighty Wind.” Guest’s astoundingly talented troupe, severalof who were also in “Guffman” and “Best in Show,” have afrightening job and do it well.

After Guest and Levy’s outline, they are leftto extend their characters, and they all do a wonderful job. A fewstand out from the pack. Coolidge, while she has very few scenes,provides many laughs as a dim-witted representative. Willard onceagain steals the show, as he did in “Best in Show,” as a managerwho is always out for money, not quality, and amuses himself byspouting stupid catchphrases from an awful TV show he once starredin.

Overall, “A Mighty Wind” is an excellent filmthat uses great writing and acting to create a truly enjoyableexperience.