‘A lot was stolen from Mozart’, said an audience member to Richard Strauss after a Rosenkavalier performance. Unmoved, Strauss replied: ‘Well, do you know anyone better?’ And indeed, Mozart is the best teacher in opera. One can learn everything from him. Above all, one cannot cheat with him. If a singer chooses Mozart for an audition, his strengths and weaknesses will be obvious after just a few bars. Murphy's Law applies all too well in Mozart: what can go wrong, often will. Stylistically, he's hard to characterize. Often, what he does is little different from his contemporaries, and yet he constantly turns convention into revolution. However brilliant new ideas and concepts might be, they won't help with Mozart. All one has to do is already in the score. All elements for a good performance can be found in it. ‘It's simple, but simple is difficult’ (Goethe). Mozart's simplicity is the most difficult of all. Only stagecraft and integrity can help here. ‘The heart ennobles the man’ is the best-known quote from his letters.

Whole libraries can be filled with what has been written about Mozart. It seems that everything has already been said. But in fact, little has been said about what ‘opera-makers’ can learn from him. And the lessons Mozart can teach are well-nigh inexhaustible. Here's a few of them.

In Mozart, a lot of things happen very quickly – in comparison to other composers, many more things happen in Mozart at any given time. His rapid shifts in musical expression and his abrupt emotional changes demand an extremely fast, inner ‘switching speed’ in order to anticipate the next phrase that already has different music. ‘Mozart is a brain problem’ said John Pritchard, my longstanding music director at Cologne Opera, who was famous for his interpretations of Mozart.

For many performers, this speed is too much to handle. They can't keep up with Mozart, so they try to salvage the situation by resorting to a one-fits-all expression that ignores the ever-changing differentiation of his music. And in fact, he does demand a lot. Sometimes his musical structure changes every two bars – even every bar in some cases.