The great composer Stephen Sondheim loved puzzles, and when he died in 2021, he left one for his good friend, British super-producer Cameron Mackintosh.

Ever since Giacomo Puccini died in 1924 without finishing his last opera, “Turandot,” audiences have thrilled to its soaring melodies like “Nessun Dorma,” but also perhaps lamented the lack of a proper ending.

Soprano Anna Netrebko needs shoulder surgery and has canceled performances in Verdi’s “Nabucco” at the Vienna State Opera.