That Harmonically Incomprehensible Mozart

In the next generation [after Mozart], although Mozart's glory was now unquestioned, [author, critic, and composer] E.T.A. Hoffmann, who loved Mozart so much he changed one of his middle names from [Wilhelm] to Amadeus, was still obliged to defend him against the charge that the harmony in the operas was often so radical as to be incomprehensible for anybody except a professional musician. Hoffmann's answer was perhaps his most brilliant essay on music. He took an example of Mozart's dramatic modulation from the cemetery scene in Don Giovanni, the E-major trio, in which the stone statue nods in response to Giovanni's invitation to dinner, and the basses of the orchestra descend to a surprising and chilling C-natural.

The professional musician, remarked Hoffmann, recognizes and names the technical procedure with no difficulty: the flatted sub-mediant holds no mystery for him. The general public, on the other hand, knows nothing of the technique, but shivers with terror at the sudden harmonic effect. It is the half-educated amateur who is puzzled by the chromatic change and is not sure what to call it. The connoisseur and the completely ignorant join hands in their understanding and admiration of the drama: the pretentious amateur is left behind by the complexity of the score. It was not to the great unwashed that Mozart's scores presented problems, and it is, in fact, the most complex of his scores — the G-minor and Jupiter symphonies, Don Giovanni, The Marriage of Figaro, and The Magic Flute — that have won the greatest and most enduring popularity.

—Charles Rosen, Radical, Conventional Mozart, 1991, The New York Review of Books