Come on lads, is it only the terminally befuddled Old Git who can actually read and understand a simple question?
The lad wants to play music directly from a Mac, and also through a controller, and be able to select either option at will. His 3.5mm jack is not working, so we're looking at USB. Simples.
As I type this, one costly option springs to mind, which is to swap the controller for a Denon Prime or similar. ( Said it was costly).
Effectively my solution to this problem is to use a Surface tablet for a second playout, into a spare controller channel. Perhaps a cheap tablet/laptop might make a cost effective solution?
Now then, is it feasible to lash a sound card into the Mac to play into one mixer channel, while using the controller to play into another? That's too technical for me, so I'll pass it over to the Mac lads, cough, Wayne, cough.
Hywel, you'd better hope none of the admins see you admitting to using Spotify as a playout, as that is very, very naughty.
Spotify, and similar streaming services are not legal for public playout. I know Denon have some sort of streaming service enabled, but that's apparently OK. Again, not my area of expertise, sorry.
The whole area is a desperately grey area in many ways. Let's just hope no numpty mentions the P****b word.