About
Microtonal Notes is Prent Rodgers's ongoing project to retune Bach's chorales into just intonation — and to find out what they sound like when every chord is allowed to be genuinely in tune.
The music
The source material is a set of twelve Bach chorales, BWV 253 through 264. They are small, dense, and harmonically complete, which makes them ideal test subjects: there is nowhere for a bad tuning to hide.
Each chord is retuned to whole-number frequency ratios drawn from a tonality diamond — the structure Harry Partch used to organise his own instruments — extended here to odd limits of 17, 19, and 23. A simulated annealing search finds good candidate tunings for each chord in isolation. A Viterbi pass then picks the route through those candidates that keeps shared notes from lurching as the harmony moves. The full write-up is in the notes.
The tools
- Csound renders the audio from the tuned note data.
- Python + NumPy run the annealing and Viterbi passes.
- Blender renders the orchestra videos — nine instrument sections animated separately and composited, driven by the same data that produced the audio.
- LilyPond engraves the scores.
All of it is open, at github.com/prentrodgers/One-footed-bride-tuning.