Russell Sherman, a concert pianist known for his boldly expressive interpretations of virtually everything he played – especially works by Beethoven and Liszt – and for influencing generations of young musicians as a teacher at the New England Conservatory in Boston, died Sept. 30 at his home in Lexington, Mass. He was 93.

His wife, Wha Kyung Byun, said the cause was not yet known but that he had been in declining health for the past four years. Mr. Sherman played his last recital in 2018, performing Beethoven’s final piano sonata at the New England Conservatory, where he proudly noted that at age 88 he was still using all 88 keys of the piano.

That concert capped a performance career that began more than seven decades earlier, in 1945, when Mr. Sherman made his professional debut at New York’s Town Hall at age 15. He went on to play with the New York Philharmonic under conductor Leonard Bernstein, only to set aside his performance career and move out west in 1959 – convinced, as he later told an interviewer, that he “had nothing new or personal to say” on the piano.

For more than 15 years, Mr. Sherman abstained from public performances, immersing himself in studies of poetry, literature and philosophy while working as a piano teacher in California, Arizona and eventually in Boston, where he joined the New England Conservatory in 1967 as chair of the piano department. He remained a fixture of the school for more than half a century, teaching distinguished pianists including Leslie Amper, Marc-André Hamelin, Randall Hodgkinson, Christopher O’Riley and HaeSun Paik, the school’s current co-chair of piano.

At the same time, he rekindled his reputation as an idiosyncratic interpreter of classic works, performing intermittently – whether at small recitals or with leading orchestras – and putting out records that showcased his belief that spontaneity, range and emotional power were more important than flawlessly hitting each note.

“Whether because of his elusiveness or in spite of it,” New York Times music critic Bernard Holland wrote in 2002, reviewing a performance at the New York Society for Ethical Culture, “the aura left behind is strong: first a fierceness of imagination that makes us rethink what we know by heart, and then a physical technique allowing the most difficult music a confident sense of order and repose.”

Mr. Sherman said that he developed his playing style, with its distinctive phrasings and abrupt changes in tempo, in part “from reading how poets analyzed poetry, scanned lines, and made the accents fluctuate with different shadings and nuances.” As he told it, he was a messenger of sorts, channeling the composer’s intentions while trying to tell a story to the audience, one that could be joyous, menacing or suffused with love and longing.

In his telling, one of Liszt’s “Petrarch Sonnets” could be boiled down to a lover’s threatening message: “If you leave me, I’ll kill myself.” By contrast, he likened Roger Sessions’s 1930 “Piano Sonata” to the “musings and meditations of a Quaker family” after church.

The results of this technique could be singularly thrillingly, as when he made his triumphant return to the stage in 1975 and performed a wrist-destroying rendition of all of Liszt’s “Transcendental Études” at Alice Tully Hall in New York. The year before, he had released a complete recording of the “Études,” a dozen knotty pieces filled with extravagant arpeggios and interlocking octaves.

“Sherman’s is the kind of art that collapses critics’ categories,” music critic Richard Dyer wrote in the Times. “He shows us that the visionary passions Liszt’s music can communicate result from the composer’s conscious manipulation of rhythmic, harmonic and structural complexity. He teaches us the music.”

Mr. Sherman completed another epic recording project in 2000, when he released the last in a five-volume set of Beethoven’s 32 piano sonatas, a body of work that the German conductor Hans von Bülow once likened to the New Testament of piano repertoire.

For all the praise that was showered on his playing, some critics never came around to Mr. Sherman’s interpretations of classical works. His style was too eccentric, they said, his playing untethered at times from the score. Mr. Sherman dismissed those claims, saying that the divided reception to his work was “between those who have imagination and those who don’t.”

“I think there is a bit of the landscape painter in me,” he said in a 1989 interview. “When I teach, I often speak to my students about trees, vegetation, rocks and clouds, and about the designs and configuration of these things, or how they move in the wind. I think some of that comes though in my playing. And when listeners occasionally respond to some of my performances in a puzzled way, I detect in their reactions the questions, ‘Where is this going?’ and ‘Do I know this place?’

“If they are sympathetic, they enjoy the visit. If they are not, they feel turned off, offended and itchy.”

The youngest of four children, Russell Sherman was born in Manhattan on March 25, 1930. Buddy, as he was nicknamed, grew up at Essex House on Central Park South, where his fellow tenants included opera singer Lily Pons, who claimed to have a pet jaguar (zookeepers later identified it as an ocelot), and the temperamental pianist Clifford Curzon, whose room Mr. Sherman managed to visit in secret, aided by a maid who knew about his interest in music.

His father, a manufacturer of women’s raincoats, died when Mr. Sherman was about 19. His mother was a homemaker who encouraged him to take up the piano, after unsuccessfully trying to foist the instrument on each of his three brothers. He started playing when he was 6 and, five years later, was accepted as a student by Edward Steuermann, an associate of pianist-composers Arnold Schoenberg and Ferruccio Busoni.

From Steuermann, he learned that music was about joy and play, not just technical mastery, and developed an aversion to commercial piano playing. He took lessons while also studying the humanities at Columbia University, receiving a bachelor’s degree at age 19, in 1949.

Mr. Sherman taught at Pomona College and the University of Arizona before being recruited to the New England Conservatory by the school’s newly installed president, composer Gunther Schuller. He became a distinguished artist-in-residence at the conservatory and also taught at Harvard University and the Juilliard School in New York.

Teaching helped him find his way as a performer, he said, providing him with a steady job as he sought to refine his technique and search for a different approach to music. He later set down some of his ideas in a 1996 book, “Piano Pieces,” which described the art of performance in almost metaphysical terms. (“To know the piano is to know the universe.”) The book also drew on his interests in poetry and sports, which rivaled his love of music; in one essay, he argued that baseball player Jackie Robinson, with his nimble athleticism and inventiveness on the field, would have been a great interpreter of Liszt.

Mr. Sherman’s marriage to Natasha Koval, a pianist from present-day Ukraine, ended in divorce. In 1974, he married Korean-born pianist Wha Kyung Byun, one of his students. She later joined him on the faculty of the New England Conservatory.

“Her love, encouragement, tenderness, interest, curiosity, and delight really saved me from my own habits,” he told the Boston Globe, “and the capacity I think we all have to become ingrown, to take on a combative posture against the world.”

In addition to his wife, survivors include two sons from his first marriage, Edward and Mark.

Mr. Sherman described piano playing as an elixir of sorts, saying that even when he was teaching students who were many decades younger, he still felt like the youngest person in the room.

“Playing the piano is rejuvenating in itself,” he told NPR in 1996. “I get up, I go to work and I discover things. It’s like in an interpretation. The great conductor Furtwängler put it this way: He said, ‘What do I do? Well, the piece begins and then something happens.’ . . . I have a song in my heart, so to speak, and I just want to let it out and work with it.”