The title of this post is from "Amadeus", and according to Maynard Solomon's superb biography of Mozart, the film at that point reflects at least a partially accurate view of how Mozart's music was considered towards the end of his life:
"The later 1780s really were for him a period of consolidation, during which the splendors, challenges, and sometimes unbearable beauties of his work were being confronted and assimilated. This was not an easy process, even for sensitive or professional musicians, for whom Mozart's music was somehow profoundly disturbing in ways that could not be quite explained. 'Mozart is unquestionably a great original genius,' wrote Dittersdorf, 'and I know of no composer who possesses such an astonishing wealth of ideas. I only wish he were a little less prodigal of them. He gives his hearers no time to breathe; as soon as one beautiful idea is grasped, it is succeeded by another and a finer one, which drives the first from the mind; and so it goes on, until at the end not one of these beauties remains in the memory.' Audiences needed a little more time to come to terms with Mozart, and indeed within only two or three years Europe was gripped by an extraordinary Mozart enthusiasm, the start of which he was still able to witness."
Of course, the succession of beautiful melodies, and the startling detours they sometimes take, is exactly why we love Mozart now. But that thing about "unbearable beauty" still seems right to me. There is something almost excruciating in Mozart's music, sometimes. I'm listening to "Cosi fan tutte" a lot now, and that's what I hear in moments such as the lovers' farewell in Act I, "Soave il vento":