How could I approach making this audio plugin?

Hello,

I am trying to create a plugin similar to Ableton's live chord built-in plugin, shown here:

https://www.ableton.com/en/manual/live-midi-effect-reference/

This plugin works by pitching an incoming signal, by semitones, with a knob and sending that signal out along with the original, dry signal. The plugin has an array of knobs for various pitching for chords and some levels per each voice.

I thought I could recreate this plugin, or make a similar one, by adapting the code for the audio plugin example shown by:

audiopluginexample.PitchShifter

https://www.mathworks.com/help/audio/ug/audio-plugin-example-gallery.html

See the attached code. It was a poor attaempt, but I thought I could duplicate object properties for 7 different knobs and then add the outputs together at the end... this didn't work...

If anyone has any ideas as to how I might approach this Idea, please let me know.

Also, how would I add multiple inputs for sending multiple voices to a plugin. I understand the use of "in" for a plugin process and how it can be used for mid-side outputs; however, I am wondering, also, how to have multiple "in" inputs in a plugin's process.

Thanks!