A popular musical variety show on public radio in the United States is the inspiration for a gently funny new film directed by Robert Altman and written by the creator of the radio show, Garrison Keillor.

For more than 30 years, listeners tuned in to hear guest stars join the regular cast for a potpourri of live music and homespun humor with a mid-western twang. This show is different, though. The radio station has been sold and the new owners are pulling the plug on A Prairie Home Companion.

Garrison Keillor writes and hosts the real public radio show and in his script for the film he gave A Prairie Home Companion a host known by the initials 'G.K.' "I just always assumed there would be an actor playing me. I had hoped there would be ... and then he just didn't show up," he said.

Garrison Keillor, Lily Tomlin, Meryl Streep and Lindsay Lohan in A Prairie Home Companion

A stellar cast did show up, however, including Lily Tomlin and Meryl Streep as a country music sister act, Lindsay Lohan as Streep's morose teenage daughter and Kevin Kline as a rundown detective moonlighting as the show's security man. Much to Keillor's chagrin, these actors would often improvise instead of just reading his script. "Here you are, you've spent weeks ... literally hundreds of hours ... working on this and they, just in a twinkling of an eye," he says, "feel that they can improve on this? Where does that come from?"

The screen comedy is directed by 81-year-old Robert Altman and radio man Keillor appreciates what the veteran filmmaker did. "Robert Altman's contribution to the movie is making it move," he says. "There is motion. Things happen. My contribution is that people say words. Those are mostly mine. Robert Altman is a movie guy. I am an essayist."

Comic actress Lily Tomlin is paired with Oscar-winner Meryl Streep, who says, "I just love to sing and never get the chance."

As the action moves between backstage and the on-air radio show, there is always music and Streep says that made this film fun for her.

"The hardest thing to get over in movie-making is the stop-start-stop-start, going out to the Winnebago [trailer], coming back an hour later when the lights are set and beginning again [and] to reintegrate into the story and the world and to feel like, when people see it, that it all is a breathing entity [and] all makes sense. What this had was Rich Dworsky, this amazing musician, who has the band behind; and the music never, ever stopped. Even when the cameras were off, people would be noodling, somebody would go over, Kevin would sit down and play the piano, somebody would start singing a song ... and we never left the movie," she says.

Among the entertainers: rambunctious and ribald singing cowboys Dusty and Lefty played by screen veterans John C. Reilly and Woody Harrelson.

"It's so funny because I always think to myself. 'Woody, you just have to not go over the line in terms of the scene.' You have to be true to the scene. I try to caution myself. Man, you check out Meryl Streep and Kevin Kline and Lily Tomlin. I was in a room with some scene-grabbers you would not believe," he says. "These are classic scene-stealers. They have every trick in the book. So I thought 'okay, I don't feel so bad now.'"

All the music in A Prairie Home Companion was performed for the cameras on the stage of the Fitzgerald Theater in Saint Paul, Minnesota - home base of the actual radio show. The film's cast also includes Tommy Lee Jones as the heartless corporate official; and Virginia Madsen plays a mysterious woman who lurks backstage during the show.