I've even met some certain keyboards and synths where the MIDI IN connect was really the MIDI Out connect. Maybe they thought people wouldn't get so confused with the "Input goes to Output" situation, but that one really shouldn't exist and really creates more confusion IMO. I've encountered some MIDI interfaces where the cord ends are marked that way also.

At any rate, if I've hooked up and get no sound when I know the MIDI data is being sent to the device and am monitoring the device's output directly such as the headphone jack being used here, I will try switching those MIDI connects around just to see. It can and has solved the problem before and reversing them can cause no physical electrical damage at all. MIDI is optically isolated behind every jack by design. Eliminates the Ground Loop possibility entirely.


--Mac