If you could read his mind, what a tale his thoughts could tell. So claimed Gordon Lightfoot in his 1970 breakout hit, the song that would launch his career as one of the most consistently satisfying singer-songwriters of the decade and would subsequently be recorded by some 300 other artists. There was a lot of musical confession in those days, with James Taylor, Jackson Browne, Joni Mitchell and so many others wearing their hearts on their lyric sleeves. Yet Lightfoot generally kept his mind to himself. A reserved Canadian, he played his emotional cards comparatively close to his vest, rarely...