Adaptation of the sample provided by Apple Creating Custom Audio Effects. Everything related to macOS has been removed to provide a single iOS and macOS solution. I've also reorganised the structure of the project to avoid any misunderstanding on the different sections involved in the creation of an AUv3 (Extension and Standalone App).
This project is for educational purpose only, I hope it will provide a better understanding about how to build an AUv3 without the overhead of creating two UIs (UIKit and AppKit) for the same project.