Director Robert Altman and writer Garrison Keillor join forces with an all-star cast to create a comic backstage fable, “A Prairie Home Companion,” about a fictitious radio variety show that has managed to survive in the age of television. Meryl Streep and Lily Tomlin star as the Johnson Sisters, Yolanda and Rhonda, a country duet act that has survived the county-fair circuit, and Lindsey Lohan plays Meryl’s daughter, Lola, who gets her big chance to sing on the show and then forgets the words. Kevin Kline is Guy Noir, a private eye down on his luck who works as a backstage doorkeeper, and Woody Harrelson and John C. Reilly are Dusty and Lefty, the Old Trailhands, a singing cowboy act. Add Virginia Madsen as an angel and Tommy Lee Jones as the Axeman and Maya Rudolph as a pregnant stagehand and Keillor in the role of a hangdog emcee, and you have a playful story set on a rainy Saturday night in St. Paul, Minnesota, where fans file into the Fitzgerald Theater to see “A Prairie Home Companion,” a staple of radio station WLT, not knowing that WLT has been sold to a Texas conglomerate and that tonight’s show will be the last. Shot entirely in the Fitzgerald, except for the opening and closing scenes which take place in a nearby diner, the picture combines Altman’s cinematic style and intelligence and love of improvisation and Keillor’s songs and storytelling to create a fictional counterpart to the “A Prairie Home Companion” radio show. The film uses the musicians and crew and stage setting of the actual radio show, heard on public radio stations coast to coast for the past quarter-century (and which, in real life, continues to broadcast). The result is a compact tale with a series of extraordinary acting turns, especially Kevin Kline’s elegant Keaton-esque detective and Lily Tomlin and Meryl Streep’s singing (“Goodbye to My Mama”) and their beautiful portrayal of two sisters who talk simultaneously. And Virginia Madsen’s serene angel. And Lindsay Lohan’s version of “Frankie and Johnny”.