Claude Frank, 89, a pianist much admired for interpretations elegantly perched between penetrating expressivity and rigorous intellectual inquest, died Saturday, Dec. 27, at his home in Manhattan, said his daughter, violinist Pamela Frank. He had suffered from dementia in recent years.

Mr. Frank was an influential performer and pedagogue, teaching at Yale University for nearly four decades, and a member of the Curtis Institute of Music faculty since 1988.

He made his New York Town Hall debut in 1950 - he had played Times Hall earlier - and, after performing with Leonard Bernstein and the New York Philharmonic in 1959, appeared with nearly every important orchestra in the United States and Europe.

His complete LP recording of the Beethoven 32 piano sonatas for RCA in 1971 (later rereleased on CD) is cherished by aficionados and was one of Time magazine's 10 best.

As an educator, he was a link between vastly different eras: student of Artur Schnabel and teacher of Richard Goode, Ian Hobson, Natalie Zhu, and dozens of younger pianists.

Born Claus Johannes Frank (the "Johannes" after Brahms, loved by Mr. Frank's mother) to a Jewish family on Dec. 24, 1925, in Nuremberg, he moved to Brussels at 12, and then to Paris, where he studied at the Paris Conservatoire. When the Nazis occupied France, he and his family took flight.

His escape from Europe in 1940 and 1941 was slow and treacherous, but wherever he found himself - in Amélie-les-Bains, St.-Paul-de-Fenouillet, or Madrid - he always found a way to stop for a few hours to play a hotel or bar piano. Practice paid off: He credited music with saving his life and those of his parents.

"In Madrid, I was practicing piano all the time, and word got around there that there was a boy of 14 who played like a son of a bitch," wrote Mr. Frank in an as-yet-unpublished account of his life with coauthor Ellen Hawley Roddick. "One day, my parents got a telephone call from the Brazilian ambassador to Spain, asking, 'Is your son free tonight?' "

It was there, playing a Brahms waltz and a Beethoven sonata at the ambassador's party, that he was heard by the American consul, who arranged a visa for him and his family to enter the U.S.

After high school in New York, he entered Columbia at 16, studying composition and conducting. He was drafted into the Army at 18 and sent first to Germany, then to Japan. After the war, in 1947, he studied with Serge Koussevitzky at Tanglewood in Massachusetts.

His rise was steady rather than meteoric. A recital in 1952 drew the attention of the New York Times: "An off night on the part of a talented young pianist. . . . Mozart is not in his style," wrote Harold C. Schonberg. But pianist was to prove critic wrong. Mr. Frank was heavily involved in Lincoln Center's Mostly Mozart Festival, performing more than three dozen Mozart works over three decades starting in 1966, and he consistently took flight in the Mozart concertos and sonatas that were the core of his identity.

"A pianist of a grand envergure, he has earned merited encomiums for his sensitive interpretations of the classics," Nicolas Slonimsky wrote in his Baker's Biographical Dictionary of Musicians.

Others heartily concurred. Mr. Frank was never held in awe for technique - he himself dismissed accuracy as subordinate to expression - but other qualities burned brightly.

"He argued, while often struggling for notes, that to admire the kind of great technique common today is to miss more important matters," this critic wrote in 2009 of Mr. Frank's final Philadelphia performance at the American Philosophical Society. "His supreme legato delivered Mozart's Piano Sonata in C Major (K. 330) from the realm of the amateur to sage status. I'd trade any pianist's last few bars of the singing second-movement 'andante' for Frank's poetry, giving the thematic material a closing both hushed and majestic."

A warm man of courtly mien, Mr. Frank could often be found in the company of artistically sympathetic partners - the Guarneri, Juilliard, Cleveland, Emerson, Mendelssohn, and Tokyo Quartets, and the London Mozart Players. His wife, pianist Lilian Kallir, who died in 2004, was a frequent co-recitalist, making what was billed as their Philadelphia debut in 1966 at the Theatre of the Living Arts on South Street. They had caught sight of each other for the first time in Portugal during the war when each was awaiting passage to the United States, but they did not speak to each other until years later.

His other steady musical partner was his daughter, with whom he often performed Beethoven and Brahms violin sonatas.

"From the first notes, there was the constant reminder of the security of their collaborative viewpoint, the refreshing buzz of the interplay between idea and response, and their obvious pleasure at uncovering some nuance or emphasis that sent the music spinning," an Inquirer critic wrote of a 2001 Philadelphia Chamber Music Society recital.

The society and its sister organization, Marlboro Music, were among Mr. Frank's deepest musical associates - he and Kallir married in Marlboro in 1959, and he performed with both groups from their near-beginnings, in 1988 and 1951, respectively. He spent 19 summers at Marlboro between 1953 and 1990, and appeared with the society a dozen times, alone or in ensembles.

Although he played music as progressive as Roger Sessions' Piano Sonata No. 2, Ginastera, and works of Schnabel, Mr. Frank concentrated on - and found his most revelatory interpretations in - core classical repertoire.

"The four composers I love most, chronologically, are Bach, Mozart, Beethoven, and Schubert," he said in his autobiography. "For me, those four can do no wrong. Every note by them is holy. I present their music as if they are gifts from God, which of course they are."

In addition to his daughter, he is survived by a niece, Catherine; and nephews Thomas and Daniel. Services were private.