Possible Clues:

• They're on the Met schedule
• One such may be for car men
• La Boheme and La Traviata, say
• La Scala offerings
• Ring quartet
• Might the car get men for one of them?
• "Einstein on the Beach" and "Nixon in China"
• Musical works, in historical times, introduced by old piano
• Works like Romeo and Juliet, Othello and Hamlet, for example
• Work times are long for such as 12 across