Please see the following article:

Link: Mastering YC: Connecting External Keyboards

Thanks Bad Mister, that is indeed a fantastic link with additional explanations.

Can you add something about my question 2 and/or 3?
Cheers,
Peter

Sorry Peter but you have exceeded your limit of questions (1) for a single session. Kidding.

I tried 20 times to midi the Fantom to the YC and it never would work correctly. It would only play the voice in channel one or something.

My advice: Get a Fantom and/or the SKPRO in March. I've been a Yamaha guy for 40 years but they are off the rails with this new management and dark order.

I own the YC61 but the OS update wasn't much to talk about and Yamaha made this thing to be way to limited. SKPRO will bury it and I've never owned a Hammond but will in March.

If I'm wrong I will come back and say so here but the SKPRO looks to be extremely versatile capable of playing 10 (Organ+ Mono Synth+ (4) part Ensemble/Piano 1 + (4) part Ensemble/Piano 2) parts simultaneously not that you need them all, custom storage for 4 engine created voice types and a real tilted color display that you can actually read etc.

Question 2
I can also loop the YC61 to the CP73 via the analog out and input respectively and come out of the set analog balanced (XLR) as the YC61 has only unbalanced outputs. This connection will be short, leaving the balanced out for the long run. Will this still work when the CP73 is in MIDI out mode? (and to disable the mix of of the local outputs of the CP73 I toggle off the 3 generators) .... is this correct?
In non-MIDI mode I just have two keyboard that are mixed in the analog output domain.
Can the 2ManualLo setting be part of a preset?

Yes, when you are using the CP as a MIDI controller, you can choose to use its own sounds, you can switch them off if you wish, or you could turn Local Control = Off. Which you do will depend on what else your doing.
A Live Set will store your settings.

Question 3
Does the CP73 have sounds that the YC has not?

Yes, it does. The Live Set Sounds and Voice Lists are listed in the manuals which are available for download. The CP is piano-centric (for example,includes the Bosendorfer Imperial among its acoustic pianos)... the YC is organ-centric (contains physical models of Tone Wheel organs and Rotary Speakers).

Hi Bad Mister, thanks again for your reply.
The SKPro is another €1000 more expensive and I like to do more than just Organ, but a nice piece indeed.
Cheers,
Peter

Peter, FYI - an article covering the SK Pro has the following title:

Hammond’s SK Pro stage keyboard isn’t just an organ - it’s a synth as well

Deciding on price is fine - I just wanted to chime in to help curb what may be a misconception.

I tried 20 times to midi the Fantom to the YC and it never would work correctly. It would only play the voice in channel one or something.

YC61 puts all of its sounds on a single MIDI channel (which also means it only receives on one channel). But even though all the sounds are on the same MIDI channel, you can still selectively choose which of those sounds you want an external board to trigger. By default, an external board will play the same sounds that are assigned to the internal keys. But based on the External Keyboard section of the manual (pages 45-46), you can independently have Keys A or Keys B or an upper or lower Organ manual triggered only by the external keys. Pretty much any combination you can think of, in terms of splitting its organ/keysA/keysB sounds across the 2 keyboards, can be accomplished with the settings described there.

As for the SK Pro, that does look like a nice board. But there are always trade-offs. It's 25% pricier ($2500 vs $2k), and you lose almost all the front panel effects controls. So you gain some things, you lose others...

But based on the External Keyboard section of the manual (pages 45-46), you can independently have Keys A or Keys B or an upper or lower Organ manual triggered only by the external keys. Pretty much any combination you can think of, in terms of splitting its organ/keysA/keysB sounds across the 2 keyboards, can be accomplished with the settings described there.

It is a pretty handy feature. It's nice too that these configurations are not globally set...i.e. you can have them change per Live Set. I just did a quick three part set up using the YC with my PX 5S....I appreciated the simplicity of it. I'm planning ahead for a July gig and I will definitely use this feature.

If you want to use the YC for recording or sequence playback, the one MIDI channel limitation becomes more problematic but using the split with some creative adjustments of octave ranges and the like you at least can get two separate but simultaneous sounds on one MIDI channel. Further, looks like the YC may be upgraded to MIDI 2.0 at some point which, as I understand it, will greatly increase the MIDI capabilities and DAW integration possibilities. Yamaha's Ben Israel sent me this link and encouraged me to share it suggesting I focus the "Profiles" video in particular: https://www.midi.org/midi-articles/the-midi-association-at-namm-s-believe-in-music-week-2021 It's a lot for an old man like me to absorb...it seems like yesterday I was drilling holes in the back of my Korg PolySix to install an after-market MIDI kit.

p.s. -- I mentioned that, compared to the SK Pro, the YC61 has the advantages of price and front panel effects controls... other advantages are LED ring endless encoders, and audio over USB. And based on history, I suspect Yamaha will have the better sounding piano sound, and there's a good chance it will also be better at things like strings/brass/winds. And if Hammond is using the same action they've used on other SK models, I think many people may prefer Yamaha's action. Of course, the SK has its advantages too. The point is that each can be someone's better choice.

Yamaha might sound better on those other voices. Still deciding on either the SKpro or the Arturia Polybrute since I already have the YC73.