generate-melody.js

// --------------------------------------------------------------------------
// -- generate-melody.js
// -- initial author: Renick Bell (renick@gmail.com)
// -- initial creation date: Wed Jun 28 10:08:48 AM CST 2023
// -- contributors: Yiler Huang (yiler7777@gmail.com); Steve Wang (stevesg168@gmail.com)
// -- license: GPL 3.0
// --------------------------------------------------------------------------

//Generated a random melody and outputs an array with objects that contains notes and octaves:
function generateRandomMelody (rootNote, mode, melodyLength, octaveMin = 1, octaveMax = 12, melodyMin = 1, melodyMax = 12, chords){
    let modes = {
      ionian: [0, 2, 4, 5, 7, 9, 11],
      dorian: [0, 2, 3, 5, 7, 9, 10],
      phrygian: [0, 1, 3, 5, 7, 8, 10],
      lydian: [0, 2, 4, 6, 7, 9, 11],
      mixolydian: [0, 2, 4, 5, 7, 9, 10],
      aeolian: [0, 2, 3, 5, 7, 8, 10],
      locrian: [0, 1, 3, 5, 6, 8, 10],
      bluesScale: [0, 3, 5, 6, 7, 10],
      bluesPentatonicScale: [0, 3, 5, 6, 7, 10],
      minorBluesPentatonicScale: [0, 3, 5, 7, 10],
    };
    let modeMap = new QuantizedMap(12, modes[mode], modes[mode])
    let randomMelody;
    let randomOctaves;
        randomMelody  = A.buildArray (melodyLength, x => randomRangeInt (melodyMin, melodyMax))
        randomOctaves  = A.buildArray (melodyLength, x => randomRangeInt (octaveMin, octaveMax))
    return randomMelody.map((x, i) => {
        return {note: modeMap.nearestLookup(x % 12), octave: randomOctaves[i], rootNote: rootNote}
    })
}

//Filters melody through a musical mode:
function quantizeMelody (melody, mode){
    let quantizedMode = new QuantizedMap(mode[mode.length - 1], mode, mode)
    console.log(quantizedMode)
    return melody.map(x => {return quantizedMode.floorLookup(x)})
}

function changeNoteBy (originalNumber, changeBy, min, max){
    let newNum = originalNumber
        console.log('changeBy', changeBy)
    if (changeBy === 'same'){
        return originalNumber
    }
    else if (changeBy === 'increase'){
        return randomRange(originalNumber, max)
    }
    else if (changeBy === 'decrease'){
        return randomRange(min, originalNumber)
    }
}

//lengthen Mode array to that it can filter MIDI values:
function createModeArray(mode) {
  let modeArray = [];
//   for (let i = 0; i < 128; i++) {
    Array.from({length: 128}).forEach((x, i) =>{
        let scaleDegree = i % 12;
        if (mode.includes(scaleDegree)) {
          modeArray.push(i);
        }
  })
  return modeArray;
}
//generated by chatgpt

function generateChangeMethod (rules){
    let randomNum = randomRange(0, 99)
    let currentMin = 0
    let changeBy;
    Object.keys(rules).map(x => {
        if (changeBy !== undefined){
            return true
        }
        if (randomNum >= currentMin && randomNum < currentMin + rules[x]){
            changeBy = x
        }
        else {
            currentMin += rules[x]
        }
    })
    return changeBy
}

function randomlyGeneratingMelodiesWithRules (mode, startValue, rules, min = 0, max = 127, melodyLength = 15){
    let currentValue = startValue
    let generatedMelody = []
//     for (let i = 0; i < melodyLength; i++) {
    Array.from({length: melodyLength}, () => {
        let generatedChange = generateChangeMethod(rules)
        currentValue = changeNoteBy(currentValue, generatedChange , min, max)
        console.log('currentValue', currentValue)
        generatedMelody.push(currentValue)
    })
    let modeArray = createModeArray(mode)
    let quantizedModeArray = new QuantizedMap(modeArray[modeArray.length - 1], modeArray, modeArray)
    return generatedMelody.map(x => {return quantizedModeArray.floorLookup(x)})
}

// randomlyGeneratingMelodiesWithRules([0,2,4,7,9,11], 80, {increase: 30, decrease: 30, same: 40},50, 120, 100)