Don’t expect the master of ceremonies to get emotional when “A Prairie Home Companion” celebrates its 40th anniversary this weekend.

“I avoid getting choked up. It’s not in good taste,” said Garrison Keillor, humming and snapping his fingers Wednesday morning as he strolled the Macalester College campus in St. Paul, site of the radio show’s first live broadcast in 1974.

“You never want the audience to be concerned. I coughed during a show in Washington, D.C., recently. People listening at home probably thought, ‘Geez, is this old guy going to croak?’ ”

He’s returning to Macalester for a three-day festival marking the anniversary with a three-hour live broadcast, a giant singalong, creation of a Lake Wobegon-style “Living Flag” and other hoopla.

A Minnesota institution that reaches 4 million listeners, “Prairie Home” has been made into a movie, parodied on “The Simpsons,” graced the cover of Time and earned its creator a Peabody Award. But four decades ago, only a dozen or so people were left in the audience after several people walked out on that first broadcast at Macalester’s Janet Wallace Fine Arts Center.

“It was too fancy for us,” Keillor said, watching custodians clean carpets in the remodeled auditorium, which will play a part in the big bash. “It was a beautiful little concert hall built for classical music, and we were just this little country music show.”

Not anymore. On Wednesday, crews worked against the clock to finish building a giant erector set of a stage for Saturday’s main event, while Keillor bantered with producers and staff. He’s always taken a nonchalant approach to all the fuss, right down to his uniform of a wrinkled suit jacket, dark pants — possibly stained with the remnants of breakfast — and black shoes held together by their laces.

In many ways, he is approaching the party just like any other show — including the fact that, as of Wednesday afternoon, he hadn’t gotten around to writing any material.

“You don’t want to do it too far in advance,” said Keillor in that trademark voice that suggests an oboe getting over a cold. “If you do, it’s hard to get serious about it.”

But don’t let his public persona fool you. A work ethic drives the 71-year-old storyteller to spend roughly 16 weeks on the road, while also producing books (“The Keillor Reader” is his latest, published in May), running his Common Goods bookstore across the street from Macalester and developing his first play, expected to premiere in late September.

“If there’s any truth that hard work will get you there, Garrison is the poster boy,” said guitarist Dakota Dave Hull, a regular guest during that first season and among the 50-plus musical acts performing this weekend.

Land of 10,000 Wobegons

If Keillor is being low-key, the rest of the state is not.

Gov. Mark Dayton has declared Sunday “A Prairie Home Companion Day.” Nearly 40 communities, from Ely to Luverne, are calling themselves Lake Wobegon for the weekend.

“There are many of us who believe Minnesota is on the national map because of the persona of our state that Garrison Keillor created,” said Jane Wildung Lanphere, executive director of the Luverne Area Chamber. “Minnesota Nice isn’t just a saying. It is a badge of honor we wear because of the exposure of ‘Prairie Home Companion.’ ”

On Wednesday, Minnesota’s U.S. senators, Al Franken and Amy Klobuchar, secured a Senate resolution honoring the program. “The show is an icon,” said Klobuchar, who plans to attend Saturday’s show. “It really represents a simpler life and represents the best in people, especially as we’re coming through this flood season and seeing neighbor helping neighbor.”

Keillor remains unfazed by all of the attention. He can recall coming close to tears only twice while on air: During a Guy Noir sketch that referenced the death of U.S. Sen. Paul Wellstone two days earlier and while performing a song he dedicated to his mother.

Perhaps he’s saving up his excitement for a 50th anniversary bash?

“What an imagination you have,” Keillor said. He has no immediate plans to retire, but doubts he’ll still be at the helm a decade from now.

“It wouldn’t be a good idea. You can be a U.S. senator into your 90s — and people have — but it’s not a nice thing to watch up close.”