MIDI Fx PolyMono for Logic Pro X: Send MIDI notes of chords to a mono synth voice by voice

PolyMono.js

// PolyMono:   Play polyphonic material on external mono synths
//             Logic Pro X MIDI-FX Scripter script to separate single notes (voices) out of chords
//
// Install:    On a MIDI track click on MIDI-FX and select Scripter,
//             paste this script into the script window and hit Run Script,
//             save script as PolyMono.
//
// How to use: create a polyphonic track (e.g. a chord progression using a poly plugin), 
//             drop PolyMono Scripter MIDI-FX on the track,
//             set polyphony to max notes played at once,
//             create as many audio tracks as polyphony (with audio input of external synth set),
//             change plugin instrument to Utility/External Instrument (mono or stereo depending on your synth),
//             in the External Instrument settings set MIDI channel and audio input correctly for your synth, 
//             Loop: set voice number in PolyMono to 1,
//             arm first audio track
//             hit "[R]ecord" to record the first voice from the synth
//             repeat Loop for each voice number (2, 3, 4, ...) of your polyphony
//             mix down the tracks or create a track stack
//             done
//
// Remarks:    CC and other MIDI stuff is passed on to each voice, so filter sweeps should work nicely.
//             If your synth doesnt support MIDI sweeps, with a DC coupled interface you might be using CVs.
//             Voice assignment is done similarly to how polyphonic synths assign voices to their "voice boards".
//             You must record as many tracks as polyphony even if you play less notes.
//             When your chords vary in polyphony, voice assignment will look random.

// polyphony of the PolyMono tool
var polyphony = 4
// voice number to output (simulates voice assignment)
var voiceNumber = 1
// count the notes played so far
var noteCounter = 1

// start with first voice when transport starts
function Reset() {
  noteCounter = 1;
}

var PluginParameters = [
  {
    name: 'Voice Number', 
    type: 'linear', 
    minValue: 1, 
    maxValue: 16, 
    numberOfSteps: 15, 
    defaultValue: 1, 
    unit: '. voice'
  },
  {
    name: 'Polyphony', 
    type: 'linear', 
    minValue: 1,
    maxValue: 16,
    numberOfSteps: 15,
    defaultValue: 4,
    unit: ' voices'
  }
];

function ParameterChanged(param, value) {
  polyphony = GetParameter('Polyphony');
  voiceNumber = GetParameter('Voice Number');

  // don't let polyphony be less than voice number
  if(voiceNumber > polyphony) {
    voiceNumber = polyphony;
    SetParameter('Voice Number', voiceNumber);
  }
}

function HandleMIDI(event) {
  if(event instanceof NoteOn) {
    // check if voice number equals note counter (modulo polyphony)
    if((noteCounter - 1) % polyphony == voiceNumber - 1) {
      event.send();
    } 
    noteCounter++;
  } else {
    // send all other events unmodified
    event.send();

    // TODO: double-check if synths handle this nicely (they should!)
    // send note off events even when they do not correspond to voice number
    // if the synth cant handle this, remember the current note pitch played and then only send if pitch match
  }
}

This is where I got the idea from: https://www.logicprohelp.com/forum/viewtopic.php?f=45&t=115798#p594990

Unfortunately, I had to do everything from the start.