Could it be that this represents a system for generating music?

[Maruyama Toru]

it concerns the techniques of musical composition.

What is the essence of this methodology (creating a musical composition or something like that)? What makes it special? Can it be compared to the medieval conception of music?

Why was it necessary to hide and encrypt the music in this way? What is the point of making a music book as inconvenient as possible by styling it to look like a herbal?

I won’t stop trying to understand your point of view.

Ah, I see it now. 
Why is it written in such an obscure way? 

The reason is that the master would provide explanations through oral transmission, using the illustrations and symbols in this manuscript as a guide.

Of course, that large diagram with the nine circles—the master must have laid it out to teach his students.