I pointed out in class today the way too obvious contradiction in McLuhan's distinction of hot and cold content within a single medium (cool jazz and hot jazz). Now that I've had time to think about it, I realize that McLuhan does deal with this. In the middle of page 27, he writes:

"The jazz of the period of the hot new media of movie and radio was hot jazz... Cool jazz came in quite naturally after the first impact of radio and movie had been absorbed."