Program to convert Midi files into an array of frequencies.

midiConvert.js

var midiFileParser = require('midi-file-parser');
var MIDIUtils = require('midiutils');
var song = "hotline_bling"
var file = require('fs').readFileSync(song + '.mid', 'binary')

var midi = midiFileParser(file);

notes = [];

noteStatus = false;
var track = 0;
for(var i = 0; i < midi.tracks[track].length; i++)
{
    currentObject = midi.tracks[track][i];
    switch (currentObject.subtype) {
      case 'noteOn':
        if(!noteStatus)
        {
          // No note is being played, get the next note
          notes[notes.length] = [MIDIUtils.noteNumberToFrequency(currentObject.noteNumber), 0]
          noteStatus = true;
        }
        break;
      case 'noteOff':
      if(noteStatus && MIDIUtils.noteNumberToFrequency(currentObject.noteNumber) == notes[notes.length - 1][0])
      {
        notes[notes.length - 1][1] = currentObject.deltaTime;
        noteStatus = false;
      }
      // if(noteStatus)
      // {
      //   // A note is being played, get the off signal
      //   if(currentObject.noteNumber == notes[notes.length - 1][0])
      //   {
      //     notes[notes.length - 1][1] == currentObject.deltaTime;
      //     noteStatus = false;
      //   }
      // }
        break;
      default:
      break;
    }
}

console.log(notes);
require('fs').writeFile(song + '.rsong', JSON.stringify(notes), (err) => {
  if(err) throw err;
  console.log("Saved song to file");
});