A Prairie Home Companion, the cinematic spoof of the long-running radio program, is as risible as a powder-milk biscuit, as sweet as a slice of be-bop-a-rebop rhubarb pie...and as improbable as a Guy Noir simile. The imperturbable Garrison Keillor serves up plenty of corny jokes, tall tales and old-time music, the stock and trade of his three decades on the air, but he hangs them on a Miltonian plot that pits a seductive angel of death against a scripture-quoting bogeyman.

His fans will be delighted. Introduced on screen in boxers and bright red socks, Keillor misses no opportunity to tell a joke on himself, his genial brand of homespun humor delivered with large dollops of Midwestern good will. Which is not to say he eschews risqué material, although the most modest Lutherans will be hard-pressed to find something offensive in the film.

Robert Altman, known for his sharper sense of satire, seems perfectly comfortable working with Keillor. The 81-year-old director effortlessly alternates between the controlled chaos of backstage and the intimate exchange between performer and audience, not to mention old friends and lovers. His trademark techniques-complicated tracking shots, overlapping dialogue, the use of multiple cameras-lend themselves perfectly to the setting, but his ability to coax remarkable performances from an array of actors has rarely served him better.

For those who have never tuned to Keillor on a Saturday night, "A Prairie Home Companion" is a pastiche of old-time radio featuring a mixture of traditional American songs, storytelling and raillery. Over the show's history, certain characters have become fixtures, including the aforementioned Guy Noir (Kevin Kline hamming it up as the slapstick private eye) and crusty cowboys Dusty and Lefty (Woody Harrelson and John C. Reilly). Keillor adds new talent to the mix in the guise of the singing Johnson sisters, Yolanda and Rhonda (Meryl Streep and Lily Tomlin)-like the Carter family, notes Yolanda, only not so famous. A few regulars from the broadcast have featured roles (Tim Russell as the exasperated stage manager) or appear as themselves (musicians Robin and Linda Williams and sound-effects man Tom Keith). The Guys All-Star Shoe Band performs under the direction of Richard Dworsky, just as they do on air.

Keillor, who wrote the screenplay based on a story he developed with collaborator Ken LaZebnik, casts himself as G.K., host of a radio show that bears a striking resemblance to his own, right down to its venue, the Fitzgerald Theater in St. Paul, but with one notable difference: the station is locally owned and only modestly successful. In fact, a conglomerate based in Texas has bought WLT (the call letters stand for "with lettuce and tomato") and has sent its hatchet man (Tommy Lee Jones) to pull the plug on the station.
A wave of nostalgia overwhelming a final performance would provide plenty of dramatic tension for a normal "Prairie" broadcast, but Keillor ups the ante by introducing an ethereal woman (Virginia Madsen) wearing a white trench coat who mysteriously appears and vanishes. It turns out she has serious business with one of the performers on the bill, a grave reminder that there are worse things than closing night.

Keillor unfolds his insouciant narrative in song, the performances before the live audience commenting on the action in the wings. Whether bantering backstage or harmonizing before the microphone, Streep and Tomlin maintain perfect pitch, especially when discussing their histrionic family with Yolanda's dour daughter, Lola (Lindsay Lohan), who is called upon to fill five minutes of airtime during the film's denouement. Harrelson and Reilly hoot it up as the guitar-picking cowpokes fond of off-color humor ("Hey, Lefty, why do they call it PMS ...?"), and Kline pratfalls about the set in a double-breasted pinstriped suit plucked from Philip Marlowe's wardrobe.

It's unfair to single out these performances, excellent as they are, because everyone appears ebullient spinning yarns and warbling standards. Even Keillor, a man with no particular vocal ability, doesn't let that stop him from crooning the "Coffee Jingle" with "Prairie" regular Jearlyn Steele or belting out the "Jens Jensen's Herring Commercial" (sung to the tune of "Won't You Come Home, Bill Bailey?").

Altman, presented an honorary Academy Award earlier this year, holds the whole business together, seeming to capture the proceedings spontaneously but shaping the production in his masterful style. Think of A Prairie Home Companion as a confluence of M.A.S.H., Nashville and The Company...with a big splash of Lake Wobegon stirred in.

-Rex Roberts