These pieces can be described as a re-tuning and orchestrating the chorales from the St. John Passion into fantasias. All the orchestrations are done by aleatoric algorithms I write in python. I create several variations on each chorale, then listen to them and make modifications until I find one of each that sounds interesting. The process uses subtractive composition, which is where I create a vast array of notes, then judiciously remove over 99% of them, leaving varying degrees of density and sparseness.
The retuning is also done by algorithm. It seeks to chose pitches in each chord that minimize the numerator and denominator of the ratios between the notes. This treats all ratios with low numbers as preferable to those with higher numbers. Just for comparison purposes, each interval in the 12 tone equal temperament scale has the ratio to the next semi-tone in the scale of 2385698798484657/2251799813685248, although it is sometimes approximated as 196/185. Lower numbers make for a stronger sound. The highest ratios in these pieces is often 8/7 or 10/9, with an occasional 27/20, or 25/18 when the algorithm couldn’t find any alternative that preserved the sense of the note as the composer intended. For this I would have had to read the mind of J.S. Bach. Or give it my best guess. I chose the latter.
Here is a zip file of my current favorites:
Zip file of Fantasias on Bach Chorales from the St. John Passion for Large Ensembles
Here are the first two you can listen to here:
bwv245.15 :
bwv245.3 :
All the code is available here: https://github.com/prentrodgers/Auto_Just_Intonation
I can’t post the samples, since I don’t own the rights to them all.
