As clearly explained by the very talented Maestro Ferrarelli, and to emphasize that there can be no doubt about what he asserts, I invite you to read the topic already open in this Forum regarding the lesson of a great master:
http://www.pianoconcerto.it/forum/index.php?/topic/434-lezione-di-un-grande-maestro/
Allow me to add, here is revealed and clarified a subject that is, incredibly, still debated—one of the many that, unfortunately, contribute to making, I add, intentionally, pianism a confused and difficult subject, and which therefore lends itself to the most contradictory and, at times, bizarre theories.
Why? Does someone fear losing the hard-earned precepts, acquired thanks to laborious and expensive lessons taken from masters entrenched in their Conservatory or post-diploma classes?
I would advise them not to worry, for the simple fact that between theory (that which is explained, I add, duly explained, by the teacher to the student) and practice (the pianist), I would say, there is a sea of musicality, if you know what I mean... 🙂