Category Archives: 12-et

On the Circle-of-Fifths Rotor

Rotor titlepageThe author introduces a device that enable the rapid analysis of harmonic functions and related chores. He explains how the idea developed over time in his pursuit of ergonomics, as well as some essential features of the device.

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Terpstra-Rotor12 Terpstra-Rotor19 Terpstra-Rotor31 Terpstra-Rotor53


The Laws of Harmonics

LawsofHarmonics titlepageStarting in the middle 1980’s, around the time that I wrote up A Short List of Musical-Cosmological Monochords, I began a patient compilation of diagrams. Most of them consisted of elaborate tables showing numerous just ratios calculated in cents, as well as some speculative monochords and representations of the Harmonic Series. I meant this work to accompany a text that sums up my investigations into Harmonics. Inevitably, it reflected my interests during the seventies and early eighties – just intonation, drone-based music, and monochords. I never got around to writing the text, though I left a couple of pages of notes. After a few years I scrapped the whole project and archived it under the rather imposing heading: The Laws of Harmonics. Recently I dragged it out of its storage to reconsider the project.

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