I’m not sure what exactly you are referring to when you mention “Sympathetic resonance”, The term sounds like somebody’s trademark for a piano technology.

If you are referring to Yamaha’s trademarked VRM (Virtual Resonance Modeling) as found in the Yamaha Digital and Hybrid Pianos... no, that is not implemented in the MONTAGE series... currently that technology is not available in the Synthesizers.

Half-Dampering is totally different, most of the Synthesizers have Half-dampering, yes, and they have Damper Resonance (DSP) as an Insertion Effect (is that what you meant?) This works in conjunction with the Sustain pedal and is a part of what happens in an acoustic piano. This is found in the MOXF, Motif XS/XF and MONTAGE series - read about these piano-centric features here

"VRM" is Yamaha's cutting edge technology, as found in the CLP (Clavinova) and the AvantGrand Series, is a full fledged Physical Modeling technology reserved for these high-end digital pianos.

Many companies confuse the issue about sympathetic resonances in a piano- VRM accurately recreates this through advanced mathematical calculations, it is not just an effect, it is a number crunching bit of actual physical modeling.

VRM physical modeling—the distinctive reverberation generated by the entire body of a concert grand piano
In a grand piano, sound resonates throughout the body of the instrument, producing a rich reverberation that envelops the listener in sound. This phenomena is reproduced perfectly in the Clavinova through enhanced Virtual Resonance Modeling (VRM). The original VRM calculates the various states of the strings for each of the 88 notes on the keyboard, from one instant to the next, and timing and depth of damper pedals pressed. The enhanced VRM now also calculates aliquot resonance in the upper octaves, and the full resonance of the soundboard, rim, and frame. This technology allows for vivid, bright, richly-varied expression that reflects the limitless number of factors inherent in piano performance.

Nice way to drown the fish! We know very well what sympathetic resonance sounds the strings of a piano. Indeed Montage does not know how to do that, it's a shame. It's a synth yes, if you consider the FM part, but the other part is a sample player with acoustic piano banks is not it?
So what's the use of imitating Bosendorfer and other Steinway etc... if sympathetic resonance is not implemented?

I remember for BM that it's about making sure that the strings of the notes depressed (even if the hammer does not hit), resonate when you play another note elsewhere on the keyboard.

Excuse my English

Montage does not implement sympathetic string resonance.

"Sympathetic Resonance" is clear/specific enough - at least the 3rd hit for a search on a popular search engine returns:

https://www.dawsons.co.uk/blog/what-is-sympathetic-resonance

and second hit is the wikipedia

https://en.wikipedia.org/wiki/Sympathetic_resonance

Thanks for your replies and sorry to have replied so in late. Unfortunately logging with Firefox is at times impossible, unless I reset it and clear its cache. Now I logged in with Chrome.
My question was related to the natural "sympathetic resonance" that an acoustic piano features.
In the meantime we'll stick with half damper effect.

Let's hope that a modeling module of this sympatic reasoning phenomenon can be added during a future firmware update. This would be a significant step towards a real acoustic piano emulation.