MOS Calc

mos.js

const getMOS = (
  edo, // 平均律(オクターブ分割数)
  tonics = 7, // 音数(nLms の n+m)
  noLimit = false
) => {
  const UNKNOWN = "Unknown";
  const FAIR_ = "Fair ";
  const UNFAIR_ = "UnFair ";
  const _HAPPY_ = "Happy (-> Porcupine)";
  const _MISH_ = "Mish (-> Amity)";
  const MAVILA = "Mavila";
  const DIATONIC = "Diatonic";
  const _MAVILA_ = MAVILA + " / Anti-" + DIATONIC;
  const BIGGIE = "Biggie";
  const GRUMPY = "Grumpy";
  const PERFECT = "Perfect";
  const RICE = "Rice";
  const FATHER = "Father";
  const BUG = "Bug";
  const AUG = "Aug";
  const BICYCLE = "Bicycle";
  const MOSH = "Mosh";
  const isMOS = ({ a, b, x, y }) =>
    [
      a === tonics - b && a === (edo - b * y) / x, // a が成り立つ
      b === tonics - a && b === (edo - a * x) / y, // b が成り立つ
      x === (edo - b * y) / a, // x が成り立つ
      y === (edo - a * x) / b, // y が成り立つ
      noLimit ? true : !(Math.abs(x - y) > 8), // 実用的か
    ].every((x) => x === true);
  const getLs = ({ lCount, sCount, lPer, sPer }) =>
    `${lCount}L${sCount}s ${lPer}/${sPer}`;
  const getET = ({ lCount, sCount, lPer, sPer }) =>
    lCount * lPer + sCount * sPer;
  const getName = (ls) => {
    const { lCount, sCount } = ls;
    if (lCount === sCount) return PERFECT;
    if (lCount === 0) return UNKNOWN;
    switch (tonics) {
      case 5:
        return [, _HAPPY_, "Classic", FATHER, BUG, PERFECT][lCount];
      case 6:
        return [, _HAPPY_, RICE, AUG, BICYCLE, GRUMPY, PERFECT][lCount];
      case 7:
        return [, _HAPPY_, _MAVILA_, MOSH, _MISH_, DIATONIC, GRUMPY, PERFECT][
          lCount
        ];
      case 8:
        return [
          ,
          _HAPPY_,
          RICE,
          FAIR_ + FATHER,
          "Dim",
          UNFAIR_ + FATHER,
          BIGGIE,
          GRUMPY,
          PERFECT,
        ][lCount];
      case 9:
        return [
          ,
          _HAPPY_,
          FAIR_ + MAVILA,
          FAIR_ + AUG,
          FAIR_ + BUG,
          UNFAIR_ + BUG,
          UNFAIR_ + AUG,
          UNFAIR_ + MAVILA,
          GRUMPY,
          PERFECT,
        ][lCount];
      case 10:
        return [
          ,
          _HAPPY_,
          RICE,
          FAIR_ + MOSH,
          FAIR_ + BICYCLE,
          "Bi-equal",
          UNFAIR_ + BICYCLE,
          UNFAIR_ + MOSH,
          BIGGIE,
          GRUMPY,
          PERFECT,
        ][lCount];
    }
    return UNKNOWN;
  };
  let res = [];
  for (let a of [...Array(tonics).keys()])
    for (let b of [...Array(tonics).keys()])
      for (let x of [...Array(edo).keys()])
        for (let y of [...Array(edo).keys()]) {
          const [lCount, sCount, lPer, sPer] = [
            x > y ? a : x < y ? b : 0, // L 数
            x > y ? b : x < y ? a : 0, // s 数
            x > y ? x : x < y ? y : 0, // L 比
            x > y ? y : x < y ? x : 0, // s 比
          ];
          const abxyls = { a, b, x, y, lCount, sCount, lPer, sPer };
          if (isMOS(abxyls)) {
            res.push({
              ...abxyls,
              ls: getLs(abxyls),
              name: getName(abxyls),
              et: getET(abxyls),
              per: lPer / sPer,
            });
          }
        }
  return res.filter(
    (v, i, s) =>
      s.findIndex((e) => e.a * e.b === v.a * v.b && e.x * e.y === v.x * v.y) ===
      i
  );
};