Much more about this piece here, on Music and Math and Feelings.
Spiraling explores a non-circular intonation: rather than squeezing or stretching (“tempering”) intervals to join into the familiar cycle of twelve notes, I have rationally tuned them to the natural harmonic series — resulting in a subtly more pure intonation, and opening the possibility of playing with large-scale tonal “drift.”
A rational approach to intonation can transform a cyclical progression of chords into something more akin to a spiral — it feels cyclical, but is steadily floating away from its starting point.