Back in my classical guitar playing days, I measured the distance of the frets of the various notes and tried to figure the mathematical relationships between the notes. I was not successful (except for the full octaves, which have a multiplyer of 2 or 1/2).

I put finding out these relationships on my bucket list, and it is still there.

Anyways, I'm quite impressed that the musical theorists of those times figured out all this math, what sounds sounded nice just because of their mathematical relationship. Using seven notes of the octave somehow had these frequencies working together. Cast out those frequencies between those "frets." Then using the 12 notes between octaves, we can change keys to get another harmonious sound. It is so amazing, even if I do not understand it.

With so many natural frequencies in nature, there must be an ideal frequency our bodies prefer over others.