Nadine Sierra, Elza van den Heever, Alice Coote, and Matthew Polenzani sing the Act III quartet. Music Director Emeritus James Levine conducts an extraordinary ensemble in Idomeneo, Mozart’s early masterpiece of love and vengeance following the Trojan War on Great Performances at the Met Sunday, July 16 at 12 PM on PBS (check local listings). (In New York, THIRTEEN will air the opera at 12:30 PM).