Math and Music: The Deeper Links (1982) (opens in new tab)

IMO, the books are great but they don't go very deeply into the math of chords or relationships between chords, no. Certainly there is math coverage of intonation (JI, 12TET, etc.), which leads to "why" chords might sound the way they do as stacked intervals with more or less pure dissonance or consonance. But the "why" of progressions are a level above that yet again. So I'm sure there are better works on chords. From a guitar (but also keyboard) perspective a fascinating book is Werner Pohlert's "Basic Harmony" -- it's thick and analytical of chords and progressions. It's comprehensive though I suppose not particularly mathematical. And you probably know there is some great writing on Just Intonation which is rooted in the ratio math of "correct" intervals and chords. "The JI Primer" by David Doty is a nice short starting point on JI with references, with emphasis on the math of intervals, obviously, but it does have some coverage of stacking these into triads and beyond. If you find a pleasing rabbit hole for chord and progression math, let us know!

Very true. People who try to reduce music to math rarely succeed.

It looks like it's a simple problem, then you realise there are edge cases, then you realise the edge cases are where all the interesting detail is, then you realise your models are braindead and actually kind of useless, and then maybe you start again with a better model.

Repeat forever.