Some giants of the piano taught and plays concerts more than they were recorded...
One of the greatest pianist of the last century is certainly Heinrich Neuhaus ...
This documentary explain why :
https://www.youtube.com/watch?v=izCfrtFuYAc&t=53s
here he play Chopin concerto no 1
https://www.youtube.com/watch?v=qf_73gQr6OQ
Here the master of Lupu, Gilels and Richter and of many other great pianists play Brahms:
https://www.youtube.com/watch?v=qTrQUJ4okM4
Here the master in Rachmaninoff :
https://www.youtube.com/watch?v=so0UgBBR2VQ
He perfectly master not only tone colors and rythm but the expression power at a height reach only by a few as Sofronitsky and Nyiregyházi...
Power of expression test is done when we compare any pianist interpretation of Liszt Mephisto waltzes for example ... Nyiregyházi here transcend anyone in powerful madness expression ....
Richter cannot even compare to Nyiregyházi
Richter - 0:00 Nyiregyházi - 3:40
Comparison of Sviatoslav Richter and Ervin Nyiregyházi playing the same passage from Liszt's 'Vallée d'Obermann'.