The pianist Martha Argerich had just delivered an electrifying performance on a snowy night in northern Switzerland. Fans were lining up backstage for autographs, and friends were bringing roses and chrysanthemums to her dressing room.

But Argerich, who at 83 is still one of the world’s most astonishing pianists, with enough finger strength to shatter chestnuts or make a Steinway quiver, was nowhere to be seen. She had slipped out a door to smoke a Gauloises cigarette.

“I want to hide,” she said outside the Stadtcasino concert hall in Basel, Switzerland, shrinking beneath her billowy gray hair. “For a moment, I don’t want to be a pianist. Now, I am someone else.”

As she smoked, Argerich, one of classical music’s most elusive and enigmatic artists, obsessed about how she had played the opening flourish of Schumann’s piano concerto that evening with the Orchestra della Svizzera Italiana. (Her verdict: “not so good.”) And she became transfixed by the memory of performing the concerto for the first time, as an 11-year-old in Buenos Aires, her hometown.

There, at the Teatro Colón in 1952, a conductor whose name was seared into her memory — Washington Castro — had offered a warning. Never forget, he said: Strange things happen to pianists who play the Schumann concerto.