By ANTHONY TOMMASINI


The phenomenally gifted if wildly unconventional pianist Glenn Gould was a tangle of personal tics and complexes. Sometimes he seemed a provocateur bent on riling the public with extreme interpretations and odd behavior. Other times he came across as a fragile, fearful man, at ease only when making music.

“Genius Within: The Inner Life of Glenn Gould,” the fascinating new documentary by the Canadian filmmakers Peter Raymont and Michele Hozer, has won praise for providing insights into Mr. Gould’s eccentric character. It shows the sad progression of a brilliant, garrulous musician with a fiercely original artistic vision as he becomes increasingly obsessive and isolated. Yet it also provides valuable insights into the inner workings of Mr. Gould’s distinctive technique and unorthodox interpretive approach.

An only child, he studied piano with his mother until, at 11, he began lessons with the Chilean-born pianist Alberto Guerrero at the Toronto Conservatory. Mr. Guerrero was an advocate of a technical discipline known as finger tapping . He taught his students to hold one hand in a relaxed position on the keyboard, lightly touching the keys. With the other hand, the student would tap a fingertip enough to depress the desired key. The mechanical action of the key springing up would lift the finger back into place. The idea was to teach the fingers to play with a minimum of effort and no excess lift.

Mr. Gould sat low to the ground when he played, his preferred chair just 33 centimeters high. In this crouched posture, with his hands reaching up to the keyboard, his fingers do everything. Yet you cannot play the piano with just your fingers. Your arms, shoulders and back - even your feet must get into act as well.

That Mr. Gould’s astonishing playing lacked this bodily dimension comes through in the film, in a segment about his performance of Brahms’s D minor Concerto with Leonard Bernstein and the New York Philharmonic in 1962.

“You are about to hear a rather, shall we say, unorthodox performance of the Brahms D minor Concerto,” Mr. Bernstein began, with “frequent departures from Brahms’s dynamic indications.”

But he emphasized that there “are moments in Mr. Gould’s performance that emerge with astonishing freshness and conviction.”

The tempos in this performance are fairly broad. Yet in retrospect Mr. Bernstein must have been bothered by Mr. Gould’s other “departures” more than by the slow tempos. Brahms often wrote for the piano as if it were an orchestra. Here Mr. Gould tried to rid the piano part of orchestral thickness and purge the music of blatant expressive contrasts.

The film quotes Mr. Gould from a radio interview the next year saying he found Mr. Bernstein’s speech that night full of good spirit and thought the whole controversy was amusing.

That Mr. Gould, who died in 1982, was beloved by a circle of intimates comes through touchingly in the film. After Mr. Gould stopped giving public concerts at age 31 and confined his work to the recording studio, he spent countless hours with Lorne Tulk, an audio engineer, who carried out his painstaking editing demands, sometimes neglecting his children, he says.

One day Mr. Gould told Mr. Tulk that they should be brothers, that they should actually go to some office in Toronto and make it legal. Mr. Tulk, as he recalls in the film, gently answered, “I would love to be your brother, Glenn,” but “I have four brothers and a sister” who might want some say in the matter.

Mr. Gould thought this answer was very sweet, Mr. Tulk says. The subject never came up again.