There is interesting piece by Peter Aspden of the Financial Times attempting to explain to a friend the essence of "cool" and ending up, not surprisingly, with the man who personified the concept - Miles Dewey Davis:
He still didn’t really get it. We went on like this for a while. I wish I could have sent him to an exhibition currently running in Paris, which would have saved us both a lot of time and arcane argument. We Want Miles, at the Musée de la Musique, is a tribute to a figure who was so cool that he actually produced a work of art called Birth of the Cool, not even allowing for the pre-existence of this precious philosophical state.
Miles Davis made most of his profound announcements with a few long, sparse notes from his trumpet or flugel-horn. They spoke with uncommon eloquence, but he wasn’t bad with words either. A man of towering confidence, he knew humility. Towards the end of his career, he was asked, in a video clip shown here, whether anyone had influenced his musical style. “Not really,” he rasped, “but I used to want to quit when I was with Bird.”