MainStage Add a Loopback plug-in
The Loopback plug-in is an insert plug-in. You can use it in any type of channel strip.
Add a Loopback instance to a channel strip
Click one of the Insert slots in the channel strip you want to use Loopback on.
Choose Delay from the shortcut menu that appears, choose Loopback from the submenu, then choose Stereo from the second submenu.