By Mark Swed, Los Angeles TimesLOS ANGELES — In mid-September 2004, James Conlon, a 54-year-old New Yorker who had just completed a nine-year appointment as music director of Paris Opera, got a surprising call from Plácido Domingo, the famous tenor and head of Los Angeles Opera. Conlon was itching to return home after having spent two decades in Europe, where he had headed the Rotterdam Symphony as well as the Cologne Opera and the German city’s Gürzenich Orchestra. He seemed the most likely candidate to succeed another “Jimmy.” James Levine had become an operatic legend as music director of the...