Walter Levin, a renowned violinist, music teacher and founder of the LaSalle Quartet whose struggles with dementia were chronicled by the Chicago Sun-Times in the 2015 series “Evi & Walter: A love story in any key,” has died at 92.

Mr. Levin died Friday at the University of Chicago Medical Center. His wife Evi Levin said he was listening to music “to the last minute.”

The couple lived at Montgomery Place, a senior living community in Hyde Park, where a service will be held in September. At the service, the Ariel Quartet — whose members Mr. Levin taught — will “perform pieces he taught them,” Evi Levin said Monday.

Walter Levin in Cincinnati in 1959. | Family photo

Mr. Levin first gained fame with the LaSalle Quartet, which produced best-selling recordings for the Deutsche Grammophon label and traveled the world, doing 67 tours in 40 years.

He became equally well known as a teacher.

“He was, more or less, like a guru of all the young string quartets in Europe,” said his wife, whom he married in 1949 and who also served as his agent.

He taught music for more than 60 years, said his son Thomas Levin, a professor in the German department at Princeton University.

“He was teaching, with gusto, when he was 85,” said another son, David Levin, a professor of theater and performance studies at the University of Chicago.

The LaSalle Quartet: Walter Levin, Henry Meyer, Jack Kirstein, Peter Kamnitzer in Salzburg in a publicity photo for the Salzburg International Music Festival 1976.

At one time, the Levins divided their time between Cincinnati — where the LaSalle Quartet was in residence at the University of Cincinnati’s College-Conservatory of Music beginning in 1953 — and Switzerland. That was where the musicians rehearsed in the summertime.

After the quartet disbanded in 1989 — when Mr. Levin was 64 — he focused on teaching. He was respected — and feared.

Among his students was James Levine, the noted conductor and pianist, who was 10 when he began studying with Mr. Levin and who grew up to become music director of the Metropolitan Opera. On Monday, Levine remembered Mr. Levin as “my great teacher and great friend.”

In “Evi & Walter,” which detailed Mr. Levin’s decline and his wife’s unceasing effort to help keep the music alive in him, the conductor spoke of the time his teacher discovered he hadn’t done all of the preparation he’d been assigned as homework. Mr. Levin ended his lesson, and Levine had to sit on his instructor’s doorstep in Cincinnati until his mother picked him up.

“I never did it again,” James Levine told the Sun-Times in 2015.

“Even as an adult, I continued to seek out his reactions to my work and musical thoughts,” Levine said Monday. “He will be greatly missed.”

The conductor James Levine (left) with Evi and Walter Levin in 1966 at the annual Richard Wagner Festspiele. | File photo

He was “incredibly influential, inspiring and demanding,” said Gershon Gerchikov, a violinist with the Ariel Quartet. “Everything had to be rooted in the score.”

As tough a teacher as he was, when he dispensed a compliment, Gerchikov said, “You were in heaven.”

Thomas Levin recalled how, growing up, his parents played a challenging, “insanely esoteric” classical music version of Name That Tune.

“Not [just] what piece is that,” he said, “but which performance, who’s conducting, which singer is singing, which soloist is playing.”

In his final years, after being diagnosed with dementia in 2011 and moving to Chicago, Mr. Levin’s intimidating intensity lessened.

“As his faculties started to diminish, he became extraordinarily sweet and appreciative,” said David Levin.

His wife became his full-time caretaker. She did everything for him, from choosing his breakfast to laying out his mittens.

Walter and Evi Levin at Montgomery Place on June 17, 2015. | Ashlee Rezin / Sun-Times

Born in Germany, Mr. Levin didn’t indulge his sons with the typical trappings of a 1960s American childhood. They had, for instance, no TV. Reading and other intellectual pursuits were encouraged. He didn’t grasp the appeal of pop music or their embrace of American musical legends including James Brown and Bootsy Collins.

“We could watch ‘Hogan’s Heroes’ once in a while,” David Levin said. “We would go over to a neighbor’s house [to watch] because [star] Werner Klemperer was the son of Otto Klemperer, a famous German conductor.”

“His work, his music, his quartet was what he was engaged with primarily and his family, secondarily — or, at least, his children secondarily — at least, until we became capable of having a conversation,” Thomas Levin said. “That’s why both my brother and I became professors. Basically, we had to become intellectuals to have a conversation with my father.”

The family has been hearing from former students with a similar message — that Mr. Levin was their most influential teacher.

“He is deeply present not only in the music he has left behind but in the change that he made in the way people thought about the music they make,” Thomas Levin said. “As one of my friends said, this is a man who left the world a more beautiful place.”

Evi Levin guides her husband Walter down a hallway at their home, Montgomery Place, in 2015. | Ashlee Rezin / Sun-Times