Long after his death, Glenn Gould still lures new listeners to his piano, connecting with them on a haunting, personal level. "He feels and you feel," says young New York writer Nicole Spectre. "I can feel his pain and joy -- it touches me. He speaks directly to me." But when he was known as the world's greatest pianist in the 1950s and 1960s, just who was Gould playing for? His audience? Himself? His demanding mother? All are likely true,...