Soul can’t be autotuned, nor can the slight imperfections that distinguish a human performance from a mechanical one.
If you want to understand the physics of music, the place to start is by looking at the overtone series, and the relationships of frequencies produced by it. The relationships between notes on a diatonic scale can be written in whole-number fractions.
A note vs. its octave is a 1:2 relationship. A note vs. its fifth is a 3:2 relationship; vs. its fourth, 4:3; and so on. It is the closeness of the relationships which creates a consonant, or peaceful/at rest sound.
In physical terms, consonance is inverse to the number of times each tone has to cycle before they start at the origin (zero point on the y-axis of their sine waves) together a second time. One cycle = same note. Two cycles = octave. Three cycles = fifth. And so on.
So yes, all the notes on a diatonic scale are multiples of the original frequency, brought down (by halving frequencies repeatedly) to the same octave.
Math is not my thing, I'll admit. The most perplexing job of work I ever did was Algebra II --- I got good grades, but I never "got" what I was going. I did well-enough on the tests, stupidly.
I once had a knock-me-down experience, though, that "revealed" to me that way before Greek or Hebrew, God spoke Trigonometry.
Sang it, probably. HA.
`
`