My music is mostly based on exploring the tonality diamond, an invention of Harry Partch. His theories are beautifully explained in his book called “Genesis of a Music“. Amazon has it here. The simple idea is that you draw a diamond, in which going up and to the right, you have the overtone series. On each of those notes in the overtone series, generate tones running down and to the right on the undertone series, the mathematical opposite of the overtone series. Here’s the one I use, where each note is shown with ratios, the approximation in 72-EDO, and the note name in Sagittal notation.

What is the middle number for in your diamond?