Yes you are, but that's no problem. I do understand what you're trying to do, so I'll repeat myself in more detail as it seems I wasn't clear enough. MIDI master keyboards don't have an internal sound engine. Perhaps it's for this reason, that on some master keyboards, the midi thru/merge function is called local on/off. Yes, I know that is not the correct terminology, but I thought that I should advise you that some master boards use this incorrect terminology, so that you can check it. For a synth that might be a little unusual, but for a dedicated master keyboard it is extremely unusual (because they should be designed for the type of thing you're trying to do). Have you checked the manual and the sysex implementation? You can skip the opto but it won't hurt to leave it there :) In fact, you could just use J11 to connect them...