NEW YORK (Reuters) - Sitting in a dimly lit New York City bar wearing a trilby hat and a dark suit, no tie, singer-songwriter Leonard Cohen pauses before responding to a question about how his ideas have changed over his lengthy career. He smiles and recalls something his close friend, the late Canadian poet Irving Layton, once said. "'Leonard's mind has not been contaminated by a single idea,'" the 77-year-old Cohen quipped dryly, eliciting laughter from an audience gathered for a preview of his first studio album of new material in eight years, 'Old Ideas. ...