https://youtu.be/2Suw2Z1Uu4o In one of the many books about Beethoven , is the story of what one of his pupils, Ferdinand Ries says about Beethoven’s teaching:When Beethoven gave me a lesson he was, I might say, unusually patient. Thus he often would have me repeat a single number ten or more times. In the Variations in F major, Opus 34, I was obliged to repeat almost the entire final Adagio variation seventeen times; and even then he was not satisfied with the expression in the small cadenza, though I thought I played it as well as he did. That day I had well-nigh a two hour lesson. When I left out something in a passage, a note or a skip, which in many cases he wished to have specially emphasized, or struck a wrong key, he seldom said anything; yet when I was at fault with regard to the expression, the crescendo or matters of that kind, or in the character of the piece, he would grow angry. Mistakes of the other kind, he said were due to chance; but these last resulted from want of knowledge, feeling or attention. He himself often made mistakes of the first kind, even playing in public.”