Mozart wrote to his friend Matthias on 24 December 1791 from Budakeszi, a small town near Budapest. There – he tells his friend – he fled after faking his death: he had managed to fake it with the help of a strange corpse and a drunk doctor, he reports in a cheerful tone. He explained the reason for his escape from Viennese society of the salons and their false friends elsewhere: he intended to devote the rest of his life to an experiment whose realization he would have been denied in the previous circumstances, the creation of a “Sound Room”. From the letter: “Here is what it is: a room built with different materials, some of which absorb sound, swallow it, others throw it back and let it bounce on them until it creates a lasting sound in the room, a body of sound that lasts over time, in which the laws of acoustics bend to the will of the composer and the performer. I myself, with the help of some able acquaintances, have transported iron plates, as well as round river stones, large and small, which are found on the banks of the Danube […] A new world is opening up around us, a world created by echo and reverberation, a world very close to its origin and to the future».