Read Joseph Joachim’s rules for playing the violinmain
Near the end of his life, the old master sent these to the last of his prodigies, Franz von Vecsey:
I love the final admonition: Loud playing and quick playing alone cannot do it; at most it only dazzles the ignorant in the audience. All depends upon beautiful playing and distinct playing.
H/t to Cho-Liang Lin for spotting the poster at Juilliard.