Possible Clues:

• A French book found in the 'Music and Ideas' section
• Voltaire optimist
• 1956 Bernstein operetta
• I’d dance around as character in satire
• Leonard Bernstein operetta
• Novella one danced with
• Bernstein operetta
• Source of the line 'If this is the best of all possible worlds, what are the others?'
• Leonard Bernstein operetta, based on a novella by Voltaire
• Operetta score by 54/60 Across