Xenharmonic Chords (at 311EDO/TET) in Strudel REPL JS

xenharmonic-chords-311edo.strudel.js

const edo = 311
const semitones = Array.from(
  { length: edo },
  (_, semitone) => semitone
)
const ratios =
  semitones.map(ratio =>
    Math.pow(2, ratio/edo))

const tail = pattern =>
  pattern
  .xen(ratios)
  .sound("gm_synth_brass_2")

register('tail', tail)

const play = semitones =>
  i(slowcat(...semitones))
  .tail()

const harmonicRatios = divisor =>
  Array.from({
    length: divisor - 1
  }, (_, dividend) =>
    divisor + dividend + 1)
  .map(dividend => dividend / divisor)

const closestSemitone = (ratio, edo) => {
  if (Math.abs(ratio - 2) < 1e-10) {
    return edo
  }
  var freq = 1200 * Math.log2(ratio)
  var cents = 1200 / edo
  var ideal = freq / cents
  var close = Math.round(ideal)
  close = Math.max(0, close)
  close = Math.min(close, edo)
  return close
}

const f = i => harmonicRatios(i).map(r =>
  closestSemitone(r, edo))

// harmonic chords
const sm2 = f(2) // 3/2
const sm3 = f(3) // 4/3 ... 5/3
const sm4 = f(4) // 5/4 ... 7/4
const sm5 = f(5) // 6/5 ... 9/5
const sm6 = f(6) // 7/6 ... 11/6

$: stack(
    play([ 0, 0, 0, 0, 0 ]),
    play([ sm2[0], sm3[0], sm4[0], sm5[0], sm6[0] ]),
    play([ sm2[0], sm3[1], sm4[1], sm5[1], sm6[1] ]),
    play([ sm2[0], sm3[1], sm4[2], sm5[2], sm6[2] ]),
    play([ sm2[0], sm3[1], sm4[2], sm5[3], sm6[3] ]),
    play([ sm2[0], sm3[1], sm4[2], sm5[3], sm6[4] ]),
    play([ edo, edo, edo, edo, edo ]),
  ).slow(2)
  ._pitchwheel({ edo: edo })