Otis Redding didn't simply "play concerts." The soul giant was a human Mount Vesuvius: He erupted. Redding was at the height of his fame in March 1967, when he played these two brief shows in London and Paris. (He would die in a plane crash in December that year.) And the audience's reaction is ecstatic — it's a fair bet that few of these Europeans had ever witnessed a spectacle quite like...