The presenter David Owen Norris (no mean pianist himself) says that Arrau got his famous tone (in Beethoven) by 'pressing the keys down slowly' - even in fast notes.
Yes, I found that utterly bewildering, not least as David Owen Norris has been involved in a scientific project in Southampton investigating pianist and how they play.
I had the good fortune to hear Claudio Arrau live several times and it is absolutely true that he created a phenomenal sound. I heard the Schumann Etudes Symphoniques from the front row, and later as a student, I saw him hold the audience of the Royal Festival Hall in the palm of his hand playing the Liszt sonata. But no one seriously imagines that he is making the piano vibrate differently by pushing the fast notes down slowly! It is pseudo science of the most idiotic kind. The beauty of Arrau's sound (and that of Richter, or even Benjamin Grosvenor who I saw live last weekend) is due to the exquisite and personal voicing in all registers. Grosvenor truly makes the piano sing, but he was doing the same as a 10 year old, but then as now, he plays the melody note with tremendous boldness that the other voices support. It has nothing directly to do with how the notes are pushed down (and as we know, a piano hammer creates gradation of volume, nothing else).
In the end, I'm guessing David Owen Norris must be alluding to something else but unclear to me what!