Just Intonation WebMIDI conversion [WIP]

justIntonation

// MIDI note conversion 
// util adapted from 
// https://github.com/sole/MIDIUtils/blob/master/src/MIDIUtils.js


	var noteMap = {};
	var noteNumberMap = [];
	var notes = [ "C", "C#", "D", "D#", "E", "F", "F#", "G", "G#", "A", "A#", "B" ];


	for(var i = 0; i < 127; i++) {

		var index = i,
			key = notes[index % 12],
			octave = ((index / 12) | 0) - 1; // MIDI scale starts at octave = -1

		if(key.length === 1) {
			key = key + '-';
		}

		key += octave;

		noteMap[key] = i;
		noteNumberMap[i] = key;

	}
  
  
	function getBaseLog(value, base) {
		return Math.log(value) / Math.log(base);
	}


	var MIDIUtils = {

		noteNameToNoteNumber: function(name) {
			return noteMap[name];
		},

		noteNumberToFrequency: function(note) {
			return 440.0 * Math.pow(2, (note - 69.0) / 12.0);
		},

		noteNumberToName: function(note) {
			return noteNumberMap[note];
		},

		frequencyToNoteNumber: function(f) {
			return Math.round(12.0 * getBaseLog(f / 440.0, 2) + 69);
		}

	};
  
  
  // http://www.microtonal-synthesis.com/scale_just_intonation.html
  
  
  //
  
  
  
  //
  


// https://algoart.com/help/artwonk4/MicroTone/microtone.htm

Just

Step Key  Freq    PB Freq   Cents  PB c Note PBend  Ratio     Interval
00  69  440.0 hz  440.2 hz    0.0     0   0   0      1:1      unison
01  70  469.3 hz  469.8 hz  111.7   113   1   8     16:15     minor diatonic semitone
02  71  495.0 hz  495.4 hz  203.9   205   2   3      9:8      major whole tone
03  72  528.0 hz  528.3 hz  315.6   316   3  10      6:5      minor third
04  73  550.0 hz  550.2 hz  386.3   386   3  55      5:4      major third
05  74  586.7 hz  587.0 hz  498.0   498   4  63      4:3      perfect fourth
06  75  618.8 hz  619.2 hz  590.2   591   5  58     45:32     tritone
07  76  660.0 hz  660.2 hz  702.0   702   7   1      3:2      perfect fifth
08  77  704.0 hz  704.6 hz  813.7   814   8   9      8:5      minor sixth
09  78  733.3 hz  733.8 hz  884.4   884   8  54      5:3      major sixth
10  79  792.0 hz  792.2 hz 1018.0  1017  10  11      9:5      just minor seventh
11  80  825.0 hz  825.1 hz 1088.0  1088  10  56     15:8      classic major seventh