— Ludwig Van Beethoven German Romantic composer 1770 - 1827
Not found in Beethoven's known works. It may be a summary of the following description of Beethoven from his piano pupil Ferdinand Ries: "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."
Fuente: "When Beethoven gave me a lesson" https://books.google.com/books?id=j8RIq67v51cC&pg=PA294&dq=%22when+beethoven+gave+me+a+lesson%22&hl=en&sa=X&ved=0CBwQ6AEwAGoVChMI7Yyz0PiNyQIViDuICh1YIAzR#v=onepage&q=%22when%20beethoven%20gave%20me%20a%20lesson%22&f=false