America could use a musical Larousse—luckily, we have Yvonne Constant’s new club act, La Différence. How did “My Way,” Sinatra’s perky anthem, spring from Claude François’s  “Comme d’habitude,” a song about a character who, as Constant explains, “did absolutely nothing his way”? What about “Que reste-t-il de nos amours?,” a melancholy chronicle of lost love and youth, which caramelized into “I Wish You Love”? Constant remarks wistfully, “Americans hope for the future…the French prefer the past. I also prefer the past.”