The alternative would be trash all of your scene and effect assignments of the existing assignments. The policy to preserve what you have is, in my opinion, better than the alternative.

Given there are only so many scene buttons - and one PART can use all of them - there's not a way to "merge" in scene assignments. Same for system effects. There are two - and they are likely not the same as the new Performance's (merged in) system effects.

If you 'd rather compromise a different Performance's system effects and scene buttons - then start constructing your Performance with the Performance you're currently merging in. And instead merge in the other Performance.

I do recognize if you have unused scenes - then the instrument could, conceivably, decide to use the unused scene buttons and assign them to the merged-in PART. But this becomes complex and maybe even confusing. Therefore - the task is left to the user to decide what to do in the compromise of limited resources (effects, scene buttons, superknob control, etc).

In a Performance, I want to Add a new Performance using the "+" button, so on the upper left of the screen I see Part x Performance Merge
I've noticed that the new added Performance loses its Effects, Scenes and Control assignments, why?

Not quite true. Here’s what’s happening... when you tap “+” to Merge Performances the upper level SYSTEM EFFECTS (Reverb and Variation) and MASTER EFFECT/EQ are lost because a Performance can have only one set of SYSTEM and MASTER Effects.

System Effects recreate the room acoustics. They are much like Auxiliary Sends on a mixer — each channel of the mixer has a Send amount to these... they are “shared” Effects. All the musicians are in the same room... System Effects recreate the shared environment.
Master Effects are shared like the System Effects but you don’t get to choose individual send amounts... everybody goes through the Master Effect and Master EQ.

If your original program is an Acoustic Piano and you ask the String Orchestra to join (merge) with the Acoustic Piano, the violins, violas, cellos and basses bring their instruments but not the room they were in. They join the Piano in the room the piano is in. The Strings inherit the room acoustics of the Performance they join.

The “merged” Part(s) keep all of their Controller assignments except those concerning the Room Acoustics... each of themerged Parts keep their two Insertion Effects (as the Insertion Effects are an integral part of each instrument). All Part specific Control Assignments are maintained including those that adjust the Insertion Effects.

what should I do to avoid losing all the features of the new added performance?

If you want to bring along Scene Settings when adding to a Performance you would need to use the “Part x - Category Search” routine, not the “Part x - Performance Merge” Search routine. Here’s how:

If you wish to add a single Part to the existing Performance
Tap the “+” to add (merge) a new Part. In this case it will be a “dummy“ Part... I’ll use an “Init” Part.
On the “Part x - Performance Merge” screen, Set “Bank/Favorite” = All,
Set “Attribute” = All
Tap “Init” > then select “Init Normal (AWM2)”
Press [EXIT] to return to the Home screen... with the newly added Part *selected* (highlighted)

Tap the newly added Part‘s “Type/Name” box to see the pop-in menu > “Category Search” (Or press [SHIFT] + [CATEGORY]
This will launch the “Part x - Category Search” routine
Along the bottom of this search screen you can opt to bring along “Parameters with Part” ... Mixing, Arp/MS, Scene, Zone (Zone Settings will appear as an option only if Zone Master is activated).

_ If you are selecting a green item (Single Part Performance) that one item will now join your original Performance... replacing the “dummy”.
_ If you are selecting a blue item (Multi Part Performance) the one item designated by “Source” will be brought in to occupy and replace the “Init Normal (AWM2)” in this slot — therefore if you know you want to add a four Part Performance to your original, you would ‘merge’ four “dummy” Parts, and use the “Part x Category Search“ multiple times incrementing the Source each time.

Scene settings are memorized per Part so you would replace each by each... thus insuring the Scene settings would be maintained.

When using this method, all Part Insertion Effects, Controller assignments, Scene Settings, Zone Settings, etc. etc., will be brought along.
Again, any upper Common/Audio level settings are not brought along... there can be only one set of “room acoustics“ per Performance.

If the sound you are bringing in relied heavily on one of the System processors, say the Variation Effect, check to see if your original Performance is using it at all. Each Performance can only have one set of “shared” System and Master Effects

Extra Credit: Super Knob Assignment are held in a buffer
When you add a Part or replace a Part in an existing Performance, items linked to the Super Knob must be reviewed and then activated on an assignment by assignment basis. Here’s what that means: if your original Performance was a Single Part, and you add a new Part (either by merging or by merging then replacing) any Super Knob relationships can only be activated upon your review. The assignments are not automatically implemented. First, you must determine if you have an available Common Assign Knob with which to link it. There are 8 Common Assign Knobs. Second, you must now inform this newly edited Performance in what Part slot the newly added Part is.

In its original Home, it was Part 1, but now in its new HOME it is going to be in a different Part number, say you place it in Part 2.
Well all of the Super Knob assignments would now be wrong... it is no longer in Part 1, so what MONTAGE does is hold the programming in a buffer... You tell it what Part number and it will recall that a Control Set.

Navigate to the upper Common/Audio level of the architecture, tap “Control” > “Control Assign” > activate the “Auto Select” option (green)
.
Move Assign Knobs 1-8, one at a time - The “Display Filter” will show you what, if anything, is already assigned to each Knob... see how many are already used. Although you can assign multiple items to each Common Assign Knob, you want to look for empty Knobs first.

There can be 16 Control Sets (Destinations) on this upper Common/Audio level of the architecture... if you have available Knobs and available Destinations (There are 4 Pages each with four possible Source/Destinations) the empty assignment will appear with “+” inviting you to Add a new Destination... when you tap that “+” a default parameter appears... tap that parameter to open the field of options...

Your newly added Part is in Part 2... if you then look on the list for “Part“ > “Part 2“ you will see the PART 2 ASSIGN 1, PART 2 ASSIGN 2, PART 2 ASSIGN 3, and so on... and as you move to each one, you will see that MONTAGE has memorized all the PART Controller Assignments. It will recall them each by each... What you are doing is recalling them, as necessary.

I know this is abstract... if you have the two Performances you’d like to combine, we’d be happy to walk you through a practical application. Nothing is lost... but for reasons that will become very clear, Controller assignments must be reviewed, then activated because for everything to work Without conflicts, you want to be sure each Part is addressed one by one.
Hope that helps.

For additional details on how the three sound SEARCHES work, please see the following article:

Mastering MODX: Using Category Search

See this thread for an example of how the Super Knob assignments are preserved:
Can’t Keep Super Knob When Copying... Solved

If you need details on combine Performances pick two and we’ll walk you through it.

Bad Mister,
I've tried your suggestions step by step, following the first part of your tutorial ( excluding the extra credit part) but I've not been able to to achieve my purpose
Adding a new Performance to an existing one I still lose the settings of the two AsSw 1 & 2, the Scenes and the Super Knob, just not sure about the Insert effects of the new added parts I don't know what I'm missing

So let's try to make a practical example by applying it to two Perfomance I'd like to combine :

1 - Existing Perfomance= " My CFX Concert" a Performance created by Moessieurs on the Soundmondo App

2 - I want to add a new one to this performance: called " Mellow Harp" it has 6 Parts, with 2 AsSwitches, 3 Scenes and a SuperKnob assignment

could you try to combine them and let me know if it works for you?

First, correct me if I’m wrong... “My CFX Concert” is four Parts, and “Mellow Harp” is six Parts.

If you are attempting to combine Performances one of the fundamentals to understand is you can only have 8 Parts simultaneously.
Page 32 of your Owner’s Manual: “You can mix several different parts together in a layer, or split them across the keyboard, or even set up a combination layer/ split. Each Performance can contain up to eight different Parts. Press the [PERFORMANCE] button before playing the keyboard.”

Attempting to create a ten Part Performance will not work (not if your goal is play all the Parts simultaneously).

Fundamentals:
Mastering MODX: Performance Basics 1

Recommendation: Start with less Parts. Once you understand how it works with combining a few Parts, it’s pretty easy to expand on what you have learned... certainly the maximum is 8 Parts in a Keyboard Controlled Performance!

Ok, you're right : 10 Part Performance, not possible according to the Manual
Now I've tried another combo :
- FM Crystal Pad ----> 2 Parts +
- Mellow Harp ---> 6 Parts = total 8 Parts ( allowed)

still not working..it's very strange

in the FM Crystal Pad when I add the six new Parts for every new Part I'll create, I start from the INIT AWM2 as a dummy part and I replace the dummy with every of the six Parts of the Mellow Harp Performance, so far it is clear to me
My question is for every new Mellow Harp Part added should I select a consecutive Part as Source?
I mean, for Part 3 --> Source Part 3
Part 4 --> Source Part 4
Part 5 --> Source Part 5
Part 6 --> Source Part 6 and so on....
OR:
Part 3 --> Source Part 3
Part 4 --> Source Part 3
Part 5 --> Source Part 3
Part 6 --> Source Part 3 ??

Gluten for punishment?
Why not add the 2 Part to the 6 Part?
Lazy is a good thing, means less work, and less possibility for confusion.

I guess you Don’t like my recommendation of learning to work with a minimum of Parts so you can understand how it works?
Separate learning from actually doing something.
Learn first, then create. It’s like making a sketch before going to oils.

I have to be in a meeting — get to this later this afternoon.... please, standby!

If I had a 6 PART Performance and a 2 PART Performance -- without knowing much else about what was to go on -- I'd probably elect to start with the 6 PART Performance and then add on a 2 PART Performance to it. Why? Because a 2 PART Performance is going to, on average, have less loose ends to tie up than a 6 PART one.

Certainly there are other considerations. If some "background" (not prominent) sound takes 6 PARTs - then maybe it doesn't matter if I lose system effects or controller assignments because it gets buried in the mix enough so it doesn't matter.

Every problem is a snowflake and you have understand the different dimensions of your choices before you can make a good choice. This is where starting small can help you out. Get a grasp of what happens when combining a 1-PARTer to another 1-PARTer. Pick something different enough in character that you can really tell something is "off" when the system effects get taken away from the 2nd Performance.

...

Combining Performances
First let’s analyze the two Performances. To do this I recall each in its HOME. Play the [AUDITION] and observe.

Mellow Harp — is a six Part Performance...
Part 1 is a 2 Element Orchestral Harp. Set to sound only when both Asgn Switches 1 and 2 are Off. (This is a function of the XA CONTROL). This Part will play an Arpeggio Phrase, but only when Scene 3 is selected

Part 2 is an 8 Element CelticHarp Glissando (up). Set to sound only when Asgn Switch 1 is On. (XA CONTROL) The same gliss is repeated starting at each E. The same gliss is repeated In each octave staring at each E. This means if you want to sound a “C” gliss, pressing any “C” key will do, if you play it while holding down AsgnSw 1.

Part 3 is an 8 Element CelticHarp Glissando (down). Set to sound only when Asgn Switch 2 is On. (XA CONTROL). The same gliss is repeated In each octave staring at each E. This means if you want to sound a “C” gliss, pressing any “C“will do, if you play it while holding down AsgnSw 2.

Part 4 is a single Element Stereo French Horn. Set to sound only when the MW is raised. And in Scene 3

Part 5 is a single Element Stereo Tremolo String. Set to sound only when the MW reaches about 7/8 of the way up. And in Scene 3

Part 6 is a 3 Element Orch Harp. Set to sound only in Scenes 2 and 3 or when the Super Knob is raised

The three Scenes change the Super Knob position, change the Mix Levels (Volume, RevSend), and introduce an Arp Phrase #5 that triggers Part 1 (Scene 3)
The Assign Switches are set to “Momentary”.
Note: there appears to be some ‘leftover’ (no longer functioning) assignments. These can occur, you’ll discover when combing Parts from previously made Performances and the programmer only uses a portion of the programming. When looking at the Brass and Tremolo String Parts... you can see that they both come from a Part that had several additional Elements... but the programmer opted only to use the French Horn Element from a Brass Ensemble, and to only use the Tremolo String Element from a String ensemble Part.

Learning to explore the existing programming is the way you can learn about how things are assembled. Although the “Mellow Harp” is 6 Parts it is not a polyphony grabber at all because of the way it is programmed.

Now let’s analyze the other candidate:

“FM Crystal Pad” — is a two Part FM-X Performance, where Part 1 is the Left channel, and Part 2 is the Right channel... creating a FM-X stereo pad.
This FM-X sound uses Algorithm 14 for both Parts... Operators 1, 2, 4, 6 and 8 are Carriers (which means they produce audible sound)
Operators 3, 5, and 7 are Modulators (this means change the timbre by influencing the Operator below them.

Part AsgnKnob 1 reduces the Operator Level of the three Modulators — thus rounding the sound to a smooth tone
Part AsgnKnob 2 increases the Operator Level of the stand-alone Carrier Operators 1 and 2 ... adding a subtle whistle (pitched two octaves above the key you press)

Part 1’s Assign Knob 1 and 2 are linked to the SuperKnob
Part 2’s Assign Knob 1 and 2 are linked to the Super Knob

Assign Switch 1 increases the Variation Send (Dual Modulator) from Part 1 and Part 2
Assign Switch 2 increases the Reverb Send (HD Hall) from Part 1 and Part 2
The Assign Switches are set “Latch” — pressing the Switch will hold in the On position (when making your combinationthis will be a conflict — the AsgnSwitches the other was set to Momentary... (the behavior of these switches must be one or the other). The likely solution would be to change the FM-X programming — as changing the RevSend and VarSend can easily be done with some other Controller.

There is only the default status used in this Performance... no Scene snapshots are stored. (Making this the easy one to move).

Combining Performances
If one was going to combine these two Performances, it is extremely clear that you could work at this a long time and struggle with copying and pasting six Parts, one-by-one, onto the two Part Performance... or you could be really smart and take the shortest route (and write a new song with the amount of time and energy that you’d save) by simply merging the two Parts of the “FM Crystal Pad” into the complex six Parts of the “Mellow Harp”. Particularly, because there are no Scenes to have to copy.

Does this make sense? As I mentioned before my meeting... This is not a good example (not even to learn from)... because it’s clear even without much knowledge of the steps necessary which way would be the easy way and which way would be unnecessarily more difficult.

I’ll recommend it again. If your goal is to learn, then start simple. When we train our trainers (those folks who are located around the country teaching retailers how to use these synthesizers)... we always stress: you don’t teach someone to create a Split, before you teach them how to Layer. And you don’t teach them by diving in the deep end of the pool. Not until they’re ready.

If you can merge two Single Part Performances first, then once you have mastered that move to more difficult things. Look how much is going on in “Mellow Harp”. The multiple Parts are used to give the performer more options (more gestures/articulations).

You can copy Scene Settings into the target Performance when you are *replacing* an existing Part. Try it with two Single Part programs.

Thanks for the suggestions