Organs are typically polyphony hogs the way they work. "Evens And Odds" is no exception. Every drawbar gets its own element. Percussion too. Other misc. With A.SW2 OFF - the organ is consuming 12 elements per note. With A.SW2 ON - this turns on percussion which adds another element. If you're playing a chord with 4 notes - you're consuming 12x4 to 13x4 (48 or 52) counts of polyphony. Add to that CFX Concert Piano - it's much lighter with respect to impact on polyphony. Even though it uses 4 PARTs with "gobs" of elements - these elements and PARTs are split up by note range and velocity range. At any given time - there are only 2 elements active for a single "note". I say that because each note gets a key-off sound played which should overlap with the trailing release of the key-on note. So for key-on there is only one element active at any given time and then key off fires off another element. So for those same 4 notes played - that's 8 counts of polyphony. So we're up to 48+8 or 52+8 (56 or 60 depending on A.SW2 for the organ). Playing more notes? Say 4 in one hand, another 4 in the other. Assuming your keyboard is not split and the organ + piano are playing all 8 notes - then this is 112 or 120 notes of polyphony. That's just sitting on 8 notes - not holding down the sustain - no previous sounds overlapping with these 8 notes. 120 is pretty close to the waterline. Hold down the sustain pedal and play one more single-finger note and boom. You're past 128 if A.SW2 is ON. You're at 112+14 = 126 if A.SW2 is off. Same thing - but instead of playing one single note after playing 8 with the sustain - and you're over.

What's killing you is that organ. It'd be better for polyphony's sake to find an organ that you can't adjust the drawbars for. One that is a sampled "preset" of the sound you want. This is also where SampleRobot (guess MODX has to purchase this) would come in handy to sample even and odds so you reduce it down to a single element per note (down from 12 or 13). If you happen to have any of the drawbars all the way down (0 volume) then consider going in and turning off that element altogether. But I would really hunt around for a better organ for conserving polyphony. This one is really meant to be played by itself without other instruments given how hungry it is.

"All Bar None" is NOT an example of an organ fitting the one-active-element-per-note-for-an-organ sound. But it's a lot slimmer. It consumes 4 counts of polyphony per note (counting the key-off which I'm not sure there's overlap or not with the key-on per the release programming - so I'll round up and say 4). Maybe not the sound you're after - but just an example of something that's closer to this. This organ sound has a key-off sound. Turning this element off I don't hear a big difference. Now we're down to 3. There's an element used for the rotating speaker ON mode (mod wheel rolled UP) and another element used for the rotating speaker OFF mode (mod wheel rolled DOWN). However, they're both firing off all the time regardless so you can morph between the two modes without a hiccup. If you don't care about the rotating speaker - you can remove the mod-wheel assignment to change volumes between these elements and then kill another element (turn OFF the 2nd element). There's a rotating speaker whistle sound. I can't really hear it. I didn't really isolate the element (solo) it - but I did turn on/off the element and didn't hear any difference when the mod wheel was UP. You can kill that element. So you're between 1-2 polyphony counts per note after turning off the elements depending on if you want to have that slow/fast rotating speaker sound or not. That's a lot less than the 12-13 per note used by "Even And Odds". I'd have to keep hunting but I'm sure there's a stock organ that uses only one element out-of-the-box.

Adding ... Motif XF carried forward a lot of the programming from the XS. And a firmware update to the Montage added all of the Motif XF Voices? I believe - not sure between voices and performances - voices would be more helpful. At any rate - all of the "stuff" to create these is in MODX. I'm not sure MODX received a firmware update for this set. Not to worry - if you cannot find the names of the XS (really XF) content - then you can look for it here:

https://www.yamahasynth.com/montage-category/motif-xf-voices-in-montage

By loading the library which should give you all of the XF voices -- and many would be carry-over from the XS. Which you may be able to find an organ voice you have used in the past and would experience the same polyphony success with your MODX. That's one route. There's probably a newer organ (new this generation, not in XF/XS) which would also work - just have to hunt for it.

Thank you! I will turn the key on note off on the piano and refuce the organ to 1 element as well and see if that helps.

The key off for CFX is small potatoes - but it probably isn't adding much for yourself or your audience (I gather). If it's not necessary - just yank it. Makes sense even if it doesn't end up helping much.

Hope something you do helps. It should.

BTW: sort of a technical discussion before on polyphony and the elements. But for the readers - it's probably easier to do more real-world tests if you want to follow along.

FIRST, recall preset "CFX Concert" (that will by my PART 1-4 sound) -- it does matter the order you load these in terms of what cuts out when polyphony runs out. As an aside: PART location has an impact to note priority. Sometimes if you have a polyphony problem, you can simply try reversing the order of your sounds and place your "high side" sound on the "low side" and vice-versa. This will change the rules of what will be cutting out and may impact the instrument/sound you could stand dropping out because it's less "obvious" when this happens. Back to the easy-to-relate-to things: SECOND, press the [+] from the HOME screen and merge in "Even and Odds". Now you'll have a few more PARTs worth of the organ. This should more-or-less duplicate the OP's setup (ordering aside). THIRD: press the A.SW2 button (assignable switch #2) to turn on that percussion for the organ which eats up more polyphony. Now press your sustain pedal down (just to make things easier) - leave it pressed down. Strike the top "C" on the piano keys. This is your reference tone. The first note you play - what you're listening for cutting out. Now lower on the keyboard, slowly roll left-hand 4-notes of a chord (doesn't matter what notes) and add the right hand slowly rolling another 4 notes. You'll notice when you get to the 8th lower note (right hand pinky - assuming the pinky is playing that top note) the reference tone cuts out - that high C. It helps confirm the details discussed before.

Since we're holding notes down here - none of the key release samples enter the picture.

This isn't a problem - it's the way it is. When you drive a muscle car - you run out of gas fast. If you want high mileage - drive a more economical car. So each kind of Performance has its place and time. Understanding why things happen will help you make better choices when assembling your custom user Performances.

Speaking of economy cars - I wonder if there's a "hybrid" organ in the presets. Probably worth looking for one. One that retains drawbars but uses some AWM2 drawbars and some FM-X. The fundamental of a tonewheel is just a sine wave - just like FM-X can produce. Ran through some effects - it wouldn't sound much different than a sampled counterpart. Mix some FM-X drawbars with AWM2 ones and you probably wouldn't notice. You would gain polyphony since anything you flop over to FM-X won't steal from your piano's (assuming it's AWM2) polyphony pool. MODX has a slightly different story than Montage due to it's lower ceiling on FM-X polyphony. That's where the hybrid can be balanced for each instrument differently. Or just optimized for MODX and used for both (probably the best approach). If it doesn't exist - either in presets or on Soundmondo somewhere -- it'd be a fun programming project to take on and share.

... went back to the keyboard and there is one. Kind of light on the AWM2 side. But what'd you know, there's something called "Hybrid Organ". It's really just an FM-X organ with one tiny part that's AWM2 - the percussion sound. I was thinking something even more "interleaved" - with some sampled drawbars mixed in with FM-X ones. But there's another option if you still want "drawbar" control. By design, already out-of-the-box only one AWM2 unit of polyphony consumed per note. Nearly 100% FM-X, though. Not that that's a bad thing. That said ... this organ doesn't quite have the character sampled ones do even with the effects there. Playing with the carrier waveforms from Sine to All 1 (... or something else) and/or changing around the amp simulator effect can get you something closer if you're willing to tweak. "Drawbars" in the Hybrid organ are really the FM-X PART's assignable knobs 1-7. Knob 8 is overdrive. You can use the sliders for the FM-X part, but best to "zero out" all of the assignable knobs if you're going to do that. Zero for Knob 1 is at 12 o'clock. All the rest of the knobs 2-7 "zero out" at full counter-clockwise (the normal "zero" ). No idea why the programmer wanted the 1st drawbar to be a bipolar curve while the rest only add. All of the default levels are programmed at 0 - so no reason to subtract from the programmed value. Just makes it harder to use in the long-run.

I have a CFX Concert Piano layered with Evens and Odds organ. The Organ's volume is set at 0 until I bring it's volume up with the #5 & 6 sliders. Regardless of the volume level on the organ part, the piano drops notes lile crazy on simpld 4 note chords. Im not even playing any bass notes along with it. It sounds terrible and un-usable in any live setting. My Motif XS never did this and has the same amount of polyphony ecvept for the FM engine in the Modx. Frustado has set in!

As you have learned, individual drawbar control is expensive when it comes to polyphony of organ sounds.

But just so you know... your Motif XS did not allow you to create and play a seven Part Performance, as you have created here... and had you constructed a setup with 7 Parts on the same MIDI channel (how this had to be done on the XS) you would wind up with exactly the same issue you are having now. And fortunately, the cure to this issue would be very similar.

Without changing the two Performances you have selected to “merge”, perhaps the biggest ‘fiction’ in layering an acoustic piano with an electric organ, is how the organ behaves when you step on the Sustain pedal. “Fiction” meaning... organs do not have Sustain pedals.

Recommended: go to the Organ and turn the Receive Switch for Sustain pedal = Off.
This should elevate 98% of your problem. Organs do not have Sustain pedals. Synthesized organs (especially those programmed to 0 volume) should be set to ignore the Sustain pedal. Pianos are among the very few instruments on the planet that have a Sustain pedal. Organs do not have Sustain pedal, per se. Note duration is manually executed by holding down keys.
Press [EDIT]
Select the first of the Organ Parts (Part 5)
Touch “Mod/Control” > “Receive Switch” > Set the Sustain box = Off
Repeat for Parts 6 and 7.

Now no matter how sloppily you use the Sustain pedal while playing the acoustic piano, it will not rob notes to support the organ, which in reality does not have a Sustain pedal. You’ll learn, as all organist do, to *hold* the keys down when you want to extend the organ tone.

That said, if you wish to edit the organ further, I recommend you recall the organ “Evens and Odds” in its HOME location and analyze exactly what you like about it. Then choose to merge just those components. As pointed out component building is great for detailing an instrument, but is costly if not used properly. The Part 3 of the organ is costing 3 notes of polyphony to recreate the tiny “noises” associated with the clicking of the Keys, whistling and whirling noise of the moving speaker cabinet... how essential this is for what your playing is questionable / ask yourself “do I need this?” If the answer is “no”, then eliminate it.

I’m willing to bet you can eliminate this (and perhaps you already know this, as you say you are using only Sliders 5 & 6 when you want to bring in the organ). Delete the noises...

You could delete Part 7 (the third organ Part — saving 3 notes of polyphony for each key press) it’s not even heard but still costs you polyphony... (and you were just compounding the issue with the unnecessary Sustain Pedal). If you like the first two Parts of the Organ Performance, make sure they are sounding when they are set as you like them. And as I recommended, if you remove them from responding to the piano’s Sustain pedal, you”ll find that the 18 Elements of the Acoustic Piano can play in the same arena as the 10 Element Tone Wheel Organ... without issue.

The Acoustic Piano has 18 Elements that are spent: one note of polyphony for each Key pressed
The Organ uses all 10 of its Elements for each key pressed... playing a 10 Note chord (something rarely, if ever, done on an Organ, but represents the absolute maximum number of notes generated by an electric organ) would cost you 100 notes of polyphony.... and if you eliminate the Sustain pedal from affecting the Organ Parts, you’ll find you can play this combination without any worry. The organ will not be stealing polyphony while not being heard. And when it is heard, it has the same limit you would have on the mighty Hammond B3... where polyphony is always limited by the number of fingers on your hands.

Hope that helps simplify the issue.

Thank you guys so much for taking the time to help with this. I actually did take out the other elements in the organ as explained and the key off on the piano. I didn't think to remove the sustain on the rgan though. I found an FMX organ that was usable and I'm off to the races again! Thank you thank you!