Add another original, top-shelf movie to the Robert Altman canon.

This time he teams up with Garrison Keillor and the result is “A Prairie Home Companion,” an irresistible casserole of American music, humor of all types and quirky characters.

Altman, at 81, has more than 30 features to his credit and at least two show up routinely on critics’ best lists. We’re talking about “Nashville” and “M*A*S*H” though others could just as easily appear.

Keillor is the creator of “A Prairie Home Companion,” the public radio show that commands a faithful following through its folksy music, homespun yet sophisticated humor and Keillor’s personality.

Instead of just filming the show, Altman and screenwriter Keillor work in several fictional characters and a couple of back stories.

A fictional show is facing its last performance at the old Fitzgerald Theatre in St. Paul. Bought by a Texas partnership fronted by The Axeman (Tommy Lee Jones), the venerable institution is sentenced to the wrecking ball in order to provide space for a parking lot.

On hand for the swan song are Yolanda and Rhonda Johnson played by Meryl Streep and Lily Tomlin. They’re the last members of a family music group and Yolanda has her morbid teenage daughter (Lindsay Lohan) in tow.

Then there are Dusty and Lefty, two scruffy cowboy singers played by Woody Harrelson and John C. Reilly. Their bawdy songs and jokes rattle station management.

The story’s launched by Guy Noir one of the real radio show’s staple characters. Guy is a world-weary private eye reduced to providing security for the theater. He’s played by Kevin Kline, who lampoons gumshoes everywhere. Guy is a dapper dresser but his bumbling antics work against his image. He’s s the first one to spot the mysterious lady in white played by Virginia Madsen.

Altman brings his trademark style to the proceedings and it’s remarkably compatible with the material.

The camera is never still, moving from front to back stage so fluidly you hardly notice the transitions. Meanwhile, the characters improvise at times and overlap their conversations. This technique has annoyed some but it creates a verisimilitude that has served Altman well for decades.

Keillor plays the radio’s host, an unflappable core of serenity in the show’s unfolding chaos and he clicks with the performers front and back stage.

Altman is known for surprises but the real surprise here is Streep. She has a set of pipes that won’t quit. Put her on “American Idol.”

For that matter, the other actors fare well in the music department and Keillor has his house band along with some favorites on hand. Among them are Robin and Linda Williams from Middlebrook.

Altman has set aside his cynicism for this outing. He establishes a family reunion mood and the actors, particularly Streep, create moments of joy for themselves that seem to go beyond acting. Lohan, party bad girl and tabloid favorite, proves she can sing and handle serious material.

Though the movie has a bittersweet quality in its ruminations on the transitory nature of everything, it’s ultimately life-affirming and uplifting. Like the radio show itself.

Four stars

A Picturehouse production. At Grandin Theatre. Rated PG-13 for off-color language. One hour, 40 minutes.