cecelius2
Thanks Glyn for all this helpful information, and for the PM's that answered my questions about its MIDI mode and using a regular midi keyboard controller with traditional mod wheels to expand the KK.
For the benefit of others here is more info before I get around to updating the main post. The question was “could the modulation and pitch bend wheels on a second (non-NI) keyboard be used in place of the touch strips?” The answer is yes, I connected my old A-Pro up and I was able to use the mod and pitch-bend without issue.
I was dubious about the touch strips but in practice I have found them to be perfectly functional. The modulation strip overcomes that age old quandary, sprung or un-sprung. It can work in either mode and do a few more things besides! (But I still like the Roland style combined pitch-bend and modulation leaver on the A-Pro for faux guitar solos!)
After testing this I decided to try Vintage Organs with the two keyboard as two manuals. I set the S61 to MIDI channel 1 and the A-Pro to channel 2. With VO in MIDI split mode (you need to switch the MIDI in to OMNI too) I have the upper manual on the S61 and the lower on the A-Pro. Pre-set key switches are the lower octave of the S61 and the drawbars (for both manuals) and other controls can be controlled from the S61 encoders. Not as good as real drawbars but still pretty handy.
The swell pedal is connected into the S61 and works as intended. The sustain pedal is assigned to the rotary speed. It’s all very playable.
This is splitting hairs but it did reveal one slight issue in the way NI have it set up. On the M3 the key colour coding on the S61 does not follow the actual upper manual notes, the low octave is still lit even though it’s not relevant to the upper manual, only the lower. On the C3 and B3 organs this does not happen because the range of the two manuals is the same.