An excellent, clear presentation - well done!

Perhaps I might suggest a slight improvement? Adding labels to (at least eight of) the white keys on your piano keyboard image - with the letters C D E F G A B C' - could make that image more useful in understanding your explanations, especially for those readers with less musical training.

I'll be looking up more of your music&maths articles, to enjoy the clarity of your thought and writing some more. Thanks!

Y.A.