exapunks-midi.js

const midi = [
  // copy your notes here, like this:
  // {
  //   "name": "E3",
  //   "midi": 52,
  //   "time": 52.81666666666657,
  //   "velocity": 0.7086614173228346,
  //   "duration": 0.13333333333333286
  // }
  // I've generated them from midi file using https://tonejs.github.io/MidiConvert/
];

const step = 1 / 33;
let curtime = 0;
let notes = [];
let tracks = [[], []];
let ends = [0, 0];

for(let note of midi) {
  note.duration = Math.round((note.time + note.duration) / step) - Math.round(note.time / step);
  note.time = Math.round(note.time / step);

  if(ends[0] <= note.time) {
    tracks[0].push(note);
    ends[0] = note.time + note.duration;
  } else if(ends[1] <= note.time) {
    tracks[1].push(note);
    ends[1] = note.time + note.duration;
  } else {
    console.log("Dropping ", note);
  }
}

const toData = track => {
  let curtime = 0;
  let data = [];
  for(let note of track) {
    if(note.time > curtime){
      data.push(0, note.time - curtime);
      curtime = note.time;
    }
    data.push(note.midi, note.duration);
    curtime += note.duration;
  }

  data.push(0, 0);

  let str = "DATA";
  for(let d of data) {
    if((str + " " + d).length > 24) {
      console.log(str);
      str = "DATA";
    }
    str += " " + d;
  }
  console.log(str);
}

console.log("# TRACK 1");
toData(tracks[0]);
console.log("# TRACK 2");
toData(tracks[1]);