Grade: A–

1898: two Parisiennes and a housemaid secretly invite each other’s partners to the Paris Opera ball and… c’mon, you can guess the rest. It’s Christmas: you don’t want Götterdämmerung. You want luxury, you want tunes and you want irresponsible fun. Richard Heuberger’s waltz-operetta Der Opernball is basically a deluxe box of musical liqueur chocolates, and it’s never been easier to guzzle the lot.