If you narrow down your MSB/LSB/PC to two preset Performances (not user, not Library, not Set List) - then we can be sure to get on the same page reproducing exactly what you see.

Example (only to show what would be helpful - not indicating there's any problem with this combo):

"Going from MSB/LSB/PC

FROM - 64/0/0
TO - 64/0/150"

All presets except for one support SSS - so it should be difficult to find one that isn't working unless there's something else going on here (possible).

If this only happens on your user, library, or Set-List material - then chances are you have a Performance that violates SSS rules. Either the FROM or TO Performance uses a PART in the range of 9-16. The other possibility being that somehow there is more than just one MSB/LSB/PC message sent over MIDI and you are actually having Montage jump through two (or more) Performance changes which would cut off the sound.

Not saying this is it, but to be complete:

Then, finally, there's the matter of expectation. SSS does not make ARPs or Motion sequence continue. There are lots of "ARP"-y and "MS"-y Performances that sound totally different when you switch off the ARP and Motion Sequence. Even when SSS is working - it does not continue the motion sequence or ARP - which could be perceived as the sound cutting off. Particularly if volume was modulated and through SSS the level was reset to "0".

SSS only applies to Performances that follow the rules, do not continue ARPs/Motion Sequence, and also only continue to hold notes you held down and continue to hold down through/after a Performance switch (including ones by MSB/LSB/PC). SSS only lasts for one Performance switch. If SSS notes are held through one Performance switch, then you switch again, the original held SSS notes will be cut off.

SSS is a function of the hardware. It works when changing Performances via the front panel when the requirements are met. Whether it works when changing programs via MIDI can vary on circumstance and if your Performance programs meet the SSS requirements.

The MONTAGE, Standalone, does not address itself with MIDI when changing Performances.
If you have a situation where you are using Parts 1-8 and are transitioning to another Performance that restricts itself to Parts 1-8, and it is still not working for your needs, (I am assuming that is what you are reporting), then you might seek to explore a different method. (Please note, placing a Part in slots 9-16 will automatically prevent SSS from doing what it does to transition programs).
If SSS cannot solve your issue, then look elsewhere for solutions for moving between the instrument sounds you require.

Extra Credit:
_ If the goal is to have an external DAW control playback, the most elegant method would be to use a separate MIDI channel to provide the overlap of instruments.
_ If the goal is to send in MSB/LSB/PC messages to automate instrument sounds you are actively playing (Set List situation), it is recommended you use the Motion Control Synthesis Engine’s plethora of methods to morph/switch sounds, instead.

Clearly, MIDI messages that include a Program Change message to switch instrumentation are insufficient in accomplishing what *you* desire to accomplish. Create custom instruments by editing the Synthesizer. We have a wealth of articles and tutorials that reveal how to do such transitions. Many of the Factory Performance show off how such transitions/changes in instrumentation can take place.

Rather than look for traditional methods to solve this issue, attack it by using the new tools available. You will need to assess what your starting point and your ending point need to be, then determine the best method to get there. Look to programming skill to accomplish the change/transition. The reasons that all sound cuts off are real; they have a cause. It allows for each program using the full resources of the instrument - to do so requires a complete reset of resources. MIDI protocol assumes “fresh slate” when PC messages are used. This is exactly what technology like SSS are trying to work around. If it does not work for your current situation, I’m recommending you change the situation to suit your needs.

You have 16 Parts in a Performance, 8 of which you can link together. Each Part is the equivalent of a complete instrument.

Learn how the programmer’s built the Factory Multi-Part sounds
Do: Study how they provide different ways to transition within these multiple instrument programs.
Do: Use Performances that allow for similar transitions to what you are going for to build your own custom version
Don’t: Take a fully made Multi-Part Performance and attempt to combine it with another Multi-Part Performance, before you fully understand *how* and *why* the programmer decided to use each of the multiple Parts.
Don’t: carry unused Parts into a situation where you need to transition... get rid of portions of Factory programming you are not using.

It’s common sense to start with your own requirements and build your own versions of instruments you require.
To get the most out of the synth often requires digging in and customizing it for your specific needs. If we can help, let us know... that’s why we’re here!

Thank you Jason and BadMister!

But the problem is not in the programming of the performances but in the way Montage behaves when receiving the change commands.

Eg If I hold the sound and change the performance by tapping directly on the screen. Whether on the setlist screen or the search screen, the sound is switched without cuts.

Now if I hold the sound and change perfomance via MIDI command the sound is cut off.

The caveat is that I'm doing this with performances that I'm sure SSS is up and running.

Very strange ...

Again: If you have a situation where you are using Parts 1-8 and are transitioning to another Performance that restricts itself to Parts 1-8, and it is still not working for your needs, (I am assuming that is what you are reporting), then you might seek to explore a different method.

We would need to know what (else) in addition to MSB/LSB/PC you are sending in. Put it this way, it is not always the case that what you are experiencing happens. I can send Performance change messages to my Montage using MSB/LSB/PC and SSS works fine so therefore, it is NOT always the case that what you are experiencing happens.

In other words, if we knew more about exactly what you are using, we could then find out/figure out why your particular method is not working.
If you’d rather not explore that, perhaps an entirely different approach will do the trick.
And if you would like to explore it... then please provide the details (I’m thinking something additional is added in the message with MSB/LSB/PC... but can’t be sure because you have yet to say what’s at the other end of the MIDI connection. Perhaps an all sounds off message is included in your message. (?)

BadMister, all of my performances are configured to use only the 1-8 parts, but by making sure SSS is supposed to work via midi command I've gone into other points and figured out what's going on.

My midi command was sending the command 2 times, one by pressing the virtual button and another by releasing the button. That's why Montage cut the sound. Problem solved! Many thanks again for the help !!