No click noise from the MS-3 itself. I'm not measuring any voltage out of it, just a closed/open state.
So how are you measuring it? Using a continuity meter? I don't see how a voltmeter would give you just a closed/open state - I'd expect a high voltage (this could be any one of a number of common things, or something pretty random) and a low voltage (0v or very close to it).
The amount of current that could be drawn is another story entirely, but I suggest we don't push that and just treat it like a delicate logic output!
Tom
PS: Once you've got this thing working with the MS3'S CTLOUT, all you have to do to add MIDI is get enough Arduino code together to turn whichever MIDI message you're interested in into a pulse like the CTLOUT. That's not actually that hard since there are useful Arduino libraries that do the grunt-work. Plus about a thousand people have already done it before you, and many of those have left traces all over the interwebz, so you can nick their good ideas!