Conversation so far:
What was Anton Rubinstein's technique?
immense sonority and technical grandeur in which all too often technical sloppiness.
What did the critics say about his technique?
critic Harold C.
Schonberg describes Rubinstein's playing as that "of extraordinary breadth, virility and vitality, immense sonority and technical grandeur.

Question: Who did he learn his technique from?
Self-contained rewrite: Who did Anton Rubinstein's learn his immense sonority and technical grandeur from?