Apple MainStage 3 - Manual (Page 147)

Appendix B The Loopback plug-in 147
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
1 Click one of the Insert slots in the channel strip you want to use Loopback on.
2 Choose Delay from the shortcut menu that appears, choose Loopback from the submenu, then
choose Stereo from the second submenu.