What makes opera run? In recent years, much of the horsepower has come from the mighty two-cylinder engine of Placido Domingo and Luciano Pavarotti, whose "Three Tenors" concerts with Jose Carreras are the most profitable road show in the modern history of classical music. It has been more than a decade since the Metropolitan Opera gave an opening-night performance without one or the other performing. But few tenors sing past 60, and both men are fast approaching the inevitable end of their dual tenure at the top of the operatic heap.
Pavarotti, 63, celebrated the 30th anniversary of his Met debut...