How to set up an aggregate audio device on Mac - Loopback tutorial
An aggregate audio device is useful if you need to combine multiple audio sources for your video. In this quick tutorial, we’ll show you how to set one up using Mac’s built-in software or an app called Loopback.
Loopback - https://rogueamoeba.com/loopback
Asio 4 All (windows) - https://asio4all.org