Possible Clues:

• La Boheme and La Traviata, say
• La Scala offerings
• Ring quartet
• Might the car get men for one of them?
• Rising river for ages? What Monteverdi worked on in Venice!
• They require libretti
• Musical works, in historical times, introduced by old piano
• Work times are long for such as 12 across
• Works like Romeo and Juliet, Othello and Hamlet, for example
• Times for work for musical works (6)