The salesman pitching aluminum siding on the phone sounded strangely familiar, like a ripple echoing across storied waters. He was, in truth, the humorist, writer and radio personality Garrison Keillor best known for his monologues about a Brigadoon-like village that emerges from his mind when he holds forth on the microphone.

His sales spoof aside, Keillor chatted about the process he goes through to weave tales of the idyllic community that springs to life each Saturday. When he leans into the microphone in that familiar storyteller voice, devoted listeners halt their chores, studio musicians rest their instruments, and the radio actors set aside their scripts. His monologue is the high point of every radio show, exactly as it will play out at Wolf Trap's Filene Center this weekend.

"I wake up early Saturday morning and start to think about Lake Wobegon," he said. "Spring arrived a little late this year, so the farmers weren't able to start their planting as early as they like. The field corn is just now coming in and they're still pessimistic about the growing season.

"Activities at the local school are tapering down because the seniors are so excited about the upcoming graduation that they are no longer educable. They're waiting to escape to the big city, leaving behind men who are clueless about marriage and ladies of a certain age who frequent the Bon Marche Beauty Salon. It's a great town for nosy people interested in the lives of others."

'A Prairie Home Companion'
» Where: Wolf Trap Filene Center, 1551 Trap Road, Vienna
» When: 8 p.m. Friday, 5:45 p.m. Saturday
» Info: $45 to $60 in-house, $25 lawn; 877-965-3872;

Because Saturday's show will be broadcast live, the Wolf Trap audience must be seated by 5:45 p.m. sharp. Once it is on the air, the show will welcome the usual roundup of guest musicians, comedy sketches and skits before it's time for Keillor's newsy account of Lake Wobegon.

The lineup onstage will include regulars Tim Russell, Sue Scott and Fred Newman, along with veteran keyboardist/composer/arranger Richard Dworsky, who leads the Guy's All-Star Shoe Band. Among the special guests are harmonica genius Howard Levy, a founding member of Bela Fleck and the Flecktones, and versatile singers Aoife O'Donovan and Heather Masse, a member of the Wailin' Jennys.

"Howard is the greatest harmonica player ever," Keillor said. "I like having an astonishing virtuoso in my shows. His solos take your breath away. People are so thrilled by him they're standing up and throwing babies. We have such fun I always dread the close of each show and have to work up to it, sometimes by singing a duet with somebody. I don't want to ask, but if Aoife or Heather should invite me to harmonize with them, I won't refuse."

During the nearly four decades of "A Prairie Home Companion" on the radio, Keillor has showcased hundreds of guest musicians, comedy skits with sound effects exactly like those heard on radio shows of another era, and witty commercials for make-believe products and sponsors. The resident actors might present a humorous play or a new adventure in one of the continuing serial melodramas. They perform standing at microphones and dispose of each completed page of script by dropping it on the floor, just as old-timey radio actors did.

"I've featured many artists and am always learning something new, but one of my most surprising discoveries was Renee Fleming, the most famous opera singer in North America," Keillor said. "She really wants to sing pop songs, things like 'Till There Was You' and Leonard Cohen's 'Hallelujah.' I've also learned that New Orleans music is sort of fading away, while bluegrass is in a golden era. Doyle Lawson of the group Doyle Lawson and Quicksilver has the most astonishing vocal abilities of any young man I know. The Milk Carton Kids are absolute geniuses in close harmony and pick up where the Everly Brothers left off.

"It's still surprising that listeners keep tuning in." he said. "I have no idea what they look forward to, but they seem to retain their enthusiasm for our ongoing skits like 'Private Eye.' As for me, although I've lost interest in eating out, alcohol, and watching football, and the pleasure of the epic novel has shrunk, I realize that short-term memory loss is a great asset. Since I still enjoy what we do on the show, we'll take a cruise this summer from Barcelona to Venice with 1,200 of my closest friends, some regulars and some irregulars. Then we'll be back in the fall with another season of 'A Prairie Home Companion.' "