Possible Clues:

• Performances with librettos
• Musical works
• Works of Wagner and Puccini
• Musical works being aspiration of Cockney artist’s
• What the musicals 'Beggar's Holiday' and 'Rent' are based on
• Productions at the Met
• "Norma" and "Tosca"
• Shows with lots and lots of singing
• Writing in Aesop adaptation works on the stage
• Stage works composed as per Ring