We were expecting an extraordinary show. First, there was the symbolic choice of 3 October, the day of Germany’s reunification. Then the reuniting of two giants of Berlin’s musical scene, Harry Kupfer as stage director and Daniel Barenboim as musical director. And then there is the opera itself, Fidelio, an apologia for freedom and faithfulness, perfect for evoking the isolation of the former Eastern Bloc. The promise of a great opera moment is realised in the first bars of...