On a visit to guest-conduct the Minnesota Orchestra, Charles Dutoit speaks for the first time about his tumultuous departure from the Montreal Symphony, and about his ex-wife, pianist Martha Argerich. “Basically, Martha doesn’t play in America, except when I ask her to. Otherwise, she wouldn’t play at all. I think there are only three pianists on this level,” he said, also citing Arturo Benedetti Michelangeli and Vladimir Horowitz.