It was not only Mozart that Glenn Gould clashed with:
Leonard Bernstein with Glenn Gould. Photo by Don Hunstein, 1957; Courtesy of Sony Classical
[Glenn Gould’s] April 1962 performance of Brahms’ first piano concerto, with the New York Philharmonic and Leonard Bernstein conducting, gave rise to an extraordinary situation in which Mr. Bernstein disagreed with Gould’s interpretation so vehemently that he felt it necessary to warn the audience beforehand. (Cait Miller)
The draft with edits of Bernstein’s speech is available online. What’s more, the full performance with Bernstein’s speech to the audience is also available on YouTube. They makes for a fascinating read together:
Source: Library of Congress.
Source: Library of Congress.