WHAT you hear with Garrison Keillor is what you get. His defiantly hick and gently ironic small-town live radio variety show A Prairie Home Companion, a leisurely melange of honky-tonk piano, spoof songs, old Protestant hymns and parody commercials beamed around the world by satellite every Saturday from the F Scott Fitzgerald Theatre in St Paul, Minnesota . . . and centred around a 20-minute stand-up monologue purporting to update listeners on events in "this little town that time forgot and the decades cannot improve" . . . is how Keillor is. So hooked are Americans on this nostalgically reassuring voice from the great Heartland . . . it's been going without a break since 1974 . . . that Keillor has made the cover of Time magazine and been greeted by the Wall Street Journal as a humorist in the same rank as Mark Twain and James Thurber.

It was perhaps inevitable that Keillor and Robert Altman . . . a fellow midwesterner from Kansas City, Missouri . . . would someday get together. The result of their collaboration is the first great movie of 2007 but sadly the last great movie of Altman's wonderful career: he died last November, aged 81. Much as Keillor does in his radio show, Altman liked to create in his movies an ambience in which actors were encouraged to behave rather than perform while the camera followed them around catching revealing moments, a spontaneity of being that gives life meaning. A Prairie Home Companion was scripted by Keillor and filmed behind scenes during the last broadcast of a show, almost identical to his own and in the same theatre, which is about to be axed by a ruthless businessman (Tommy Lee Jones) who regards it as long past its prime.

"This isn't really going to be your last show, is it?" says Lindsay Lohan, who plays country singer Meryl Streep's death-obsessed teenage daughter. "Every show is your last show, " Keillor replies.

"That's my philosophy." It was Altman's, too. Prairie is rich in the spirit of carrying on regardless.

"How about just a moment of silence?" suggests Lohan, when one of the show's old-timers dies in his dressing room. "Silence on the radio, " ponders Keillor, "I don't know how that works." Neither Altman nor Keillor do sentiment.

They value the oddities that make everyone different, but they don't romanticise them. "What if you die someday, " asks Lohan. "I will die, " says Keillor. "Don't you want people to remember you?" "I don't want them to be told to remember me."

What story there is centres on two sisters played by Meryl Streep . . . giving yet another standout performance . . . and Lily Tomlin . . . an Altman regular . . . who are survivors of a four-sister country music act and have been singing the same songs for years.

Between their performances . . .and even during them through the music and ad-libbing . . . simmering passions, feuds and misunderstandings come to a head. Favourite characters from the actual show are recycled, with Kevin Kline as the security guard Guy Noir who lives his life as if he's in a Raymond Chandler thriller.

Then there's Woody Harrelson and John C Reilly as the singing cowboys Dusty and Left, hilarious in their subversive rendition of the Bad Joke song in which each tries to out do the other in bawdiness, while a worried station producer considers pulling the plug.

Virginia Madsen introduces a fresh element as a mysterious lady in a white raincoat, a potential saviour of the show who may or may not be an angel of death. "There is no tragedy in the death of an old man, " she says.

"Forgive him his shortcomings, and thank him for all his love and care."

Too often older great American directors (notably Billy Wilder) have had the plug prematurely pulled on their film-making by accountants who refuse to provide insurance because of their age.

Happily A Prairie Home Companion was made possible by Paul Thomas Anderson (whose Magnolia was inspired by Altman's Short Cuts) signing on as a back-up director prepared to take-over in case of Altman's incapacitation.

In doing so he enabled the world to enjoy the experience of seeing one of Hollywood's great outsiders to go out in his own inimitable style.