He was tall with a distinguished mustache and magic fingers. Long fingers that traveled down the Mississippi River and connected to New Orleans.

Butch Thompson was a Minnesota musical giant, the original pianist on radio's "A Prairie Home Companion," an expert on stride and ragtime piano who consulted on a Broadway musical, a pops musician who played with orchestras from Cairo to Tokyo.

"His knowledge of stride piano and the ability to perform it were unmatched," said Steve Heckler, founder of the Twin Cities Jazz Festival at which Thompson played for many years.

"In a word, Butch was a musician's musician," said Crescent City trumpeter Clive Wilson, who gigged with Thompson regularly at the New Orleans Jazz Festival. "It is hard to imagine a world of New Orleans jazz without Butch."

Thompson died Sunday of complications of Alzheimer's at his St. Paul home. He was 78.

"He wanted the end to come at home, and I was so happy I could do that for him," his wife, Mary Ellen Niedenfuer Thompson, said via e-mail. "He knew he was home, he said he wanted to play his piano … this through the fog of end-stage dementia. I'm so glad he knew he was home with me and the dogs."

The pianist performed his last concert in June 2021 at Crooners Supper Club in Fridley with the Southside Aces, a group he had gigged with since 2017. They released an album, "How Long Blues," featuring Thompson in 2020.

"There were a handful of times when we would play an improvised duet with the band, after which he would turn to me and say, in the manner of a compliment, with a smile twitching beneath his mustache, 'I never heard anything like it!' " recalled Southside Aces leader Tony Balluff, who plays clarinet, Thompson's other instrument.

Although Thompson got his professional start on clarinet as a teenager playing traditional jazz with the Hall Brothers, he rose to local prominence as the original house pianist — and later music director — on Garrison Keillor's "A Prairie Home Companion" (PHC).

"I first met him as a fellow English major at the University of Minnesota, sitting behind me in Sarah Youngblood's Shakespeare course, but he got off that road, thank goodness, and found his true calling," Keillor said via email. "We worked together for years, and I never heard a disparaging word from him nor anything confessional, two of my specialties. It was all there in the music."

Twin Cities piano maestro Richard Dworsky succeeded Thompson on PHC and played with him on PHC cruises and in the 2006 Robert Altman movie "A Prairie Home Companion.""His piano and clarinet playing were the real deal," Dworsky said. "Sometimes flashy and virtuosic and sometimes spare, slow and soulful."

Colleagues described Thompson as a humble, gentle man.

"He was very giving — he always wanted to make the audience happy — and his self-deprecation was very famous," said Michele Jansen, former general manager at KBEM-FM (Jazz 88), where Thompson hosted the weekly program "Jazz Originals" for 25 years until 2017. "He was funny, with such a dry humor."

Patty Peterson's program preceded Thompson's on Sunday evenings.

"It was astounding the amount of money he'd bring in one hour in pledges because of his popularity," she said.

Growing up in Marine on St. Croix, Richard Thompson Jr. started piano lessons at age 6. There were two pivotal moments in his childhood: seeing a movie at the village hall of a youngster, Sugar Chile Robinson, playing boogie-woogie with tiny hands; and, at his own junior high talent show in 1956, getting a rousing reaction to his boogie-woogie piano treatment of Bill Haley & the Comets' "Rock Around the Clock."

As a kid, Thompson became a serious record collector of jazz, which his father touted, as well as rock 'n' roll and R&B. His interest was further fueled by attending Minneapolis concerts by jazz star Louis Armstrong and classical piano master Arthur Rubinstein.

At Stillwater High School, Thompson pursued the clarinet, which he'd started playing in sixth grade. With some classmates, he formed Shirt Thompson and His Sleeves to play at dances.

In 1961, while attending the University of Minnesota, the clarinetist sat in with the Hall Brothers New Orleans Jazz Band of Minneapolis. A year later, he officially joined the group, playing seedy Hennepin Avenue bars even though he wasn't old enough to buy a drink. Then, two months after signing on, Thompson made his first trip to the Crescent City.

"When I got to New Orleans, I was just sold on that music," he declared in a 2020 interview.

After a two-year stint in the Army, Thompson returned to the U. Because Hall Brothers gigs couldn't pay all the bills, he toiled as a newspaper reporter and then taught ragtime piano and jazz history at the West Bank School of Music. In 1974, he began his dozen-year tenure on PHC.

The classical world also beckoned for a featured soloist at pops concerts, starting in 1987 with Thompson's performance of "Scott Joplin Suite for Piano and Orchestra." The pianist-clarinetist traveled the world, playing everywhere from Tokyo to Cairo.

Thompson released more than two dozen albums under his own name and appeared on numerous other records, including a 1996 Grammy-winning project by trumpeter Doc Cheatham.

A noted jazz historian, Thompson served as a consultant for the 1992 Broadway musical "Jelly's Last Jam," about the piano jazz of Jelly Roll Morton.

Survivors include his wife, sons Victor and Sam; stepdaughter Frannie Christensen; brothers Peter and John, sister Barbara Raff and two grandchildren. A private burial will be held in Marine on St. Croix with a public celebration of life to be scheduled later.

Star Tribune writer Chris Riemenschneider contributed to this story.