https://offtonic.com/theory/book/1.html
https://lovec-not.ru/blog/dlitelnosti-not
https://en.wikipedia.org/wiki/Scientific_pitch_notation
https://en.wikipedia.org/wiki/Piano_key_frequencies
https://en.wikipedia.org/wiki/Diatonic_scale
Читать: Маскелиаде, сс. 40..54.
https://en.wikipedia.org/wiki/Overtone
https://en.wikipedia.org/wiki/Harmonic_series_(music)
https://www.youtube.com/watch?v=cnH2ltfW48U
https://en.m.wikipedia.org/wiki/Just_intonation
Совпадения гармоник в интервалах: https://youtu.be/0lmS5lQ5MSU
https://music.stackexchange.com/questions/64910/dissonance-why-doesnt-the-roughness-curve-have-a-dip-for-complex-intervals-lik/69068