Yep, it’s all ratios, and not just melody and harmony. You can express every common harmonic interval as a superposition of simple rhythms (for example, 3 beats per measure over 4 beats per measure is equivalent to a perfect fifth), which are sped up until the oscillations are within the range of human hearing.
Interesting. I had music theory classes back in the 70s and I don’t remember anything like that. Not doubting you, I just don’t remember it being taught.
Did I miss something, or is this relatively new…