A Transit System for Your Audio
Combine Audio Sources
Configuring a virtual audio device from multiple sources is easy. Just add the applications and physical audio devices you want to include to the Audio Sources table to get started.
Your Mac will show Loopback's virtual devices exactly like physical devices. Find them listed among other devices in System Preferences or select them as an input or output in any audio app.
Send Audio Between Apps
Loopback can also create pass-thru devices, which send audio from one app to another. Set the Loopback device as the output in one app and the input in another to make audio flow directly between the applications.