Poland's Krystian Zimerman, widely regarded as one of the finest pianists in the world, created a furor Sunday night in his debut at Walt Disney Concert Hall when he announced this would be his last performance in America because of the nation's military policies overseas. Before playing the final work on his recital, Karol Szymanowski’s "Variations on a Polish Folk Theme," Zimerman sat silently at the piano for a moment, almost began to play, but then turned to the audience. In a quiet but angry voice that did not project well, he indicated that he could no longer play in...