Is it technical music theory?
Well, if it was, I sure wouldn't understand it! Yes, there is some theory in it, but he does explain most of it (he was a professor at Oxford, so he knows how to explain), and he doesn't just throw it in for the hell of it, but to make a point. As I understand from the intro, he always gave his lectures (that's what many of these are) while sitting at the piano and he would make his point by playing a lick. So, you can't do that here, so he writes it out. Still, you can get the point, and it's worth the effort just to be able to enjoy the other 90% that isn't music theory.

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Listening to:
Skærved (Violin) / Shorr (Piano) - Beethoven - Bia 550 Op 96 Sonata #10 in G for Violin & Piano 4th mvmt - Poco allegretto