[CharlesOConnell]

1. The Comma of Ptolemy plus the Schisma equals the Comma of Pythagoras, and
2. Pythagorean has purity of fifths, Quarter Comma Meantone has purity of thirds, and Equal Temperament has purity of octaves.

[Boogieman]

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.