"Paderewski plays the rhapsodies like improvisations – inspirations of the moment. It is the negation of the mechanical in music, the assassination of the metronome. When ordinary pianists play a Liszt rhapsody, there is nothing in their performance that a musical stenographer could not note down just as it is played. But what Paderewski plays could not be put down on paper by any system of notation ever invented. For such subtle nuances of tempo and expression there are no signs in our musical alphabet. But it is precisely these unwritten and unwritable things that constitute the soul of music and the instinctive command of which distinguishes a genius from a mere musician."
January 1, 1970
https://en.wikiquote.org/wiki/Metronome