I have installed Reaper on my Mac. The interrupter is connected. I see the red light. I try to play a MIDI file. If a lower or raise the volume, I can't see any change in the red light outputting from the interrupter.
On MIDI app, I see the interrupter is connected to my Mac. See the following pictures.
On Reaper, it is set up like that.
Am I setting it up properly?