Using Multiple USB Audio Devices in Garageband

Using Multiple USB Audio Devices in Garageband | Adam Weiss: Podcast Consultant: "The way to do it is through an application with the confusing name of Audio MIDI Setup (found in your Mac’s Applications ? Utilities folder). This program can be used to combine any audio inputs on your computer into one “Super Input” (called an Aggregate Device be Apple) that can be used in any program."