Change settings whilst holding notes and you will get this sort of thing and always have.
The Montage seamless switching behaviour is very impressive but the way it works is extremely hard to achieve in an arranger because of the way it works, which I think is this - based on an over The shoulder view of this being demoed so I might be completely wrong!
The Montage runs permanently in a performance mode where up to 16 layers of sound can be played simultaneously to form a single voice. That makes a hugely dense sound but as each layer is good enough for a decent sound on its own you rarely need to use that many layers to get a rich and complex voice. What the seamless crossfade does is fade down one voice which is using up to 8 layers and fade up another voice which is already loaded into the other 8 layers not currently in use. So there's no effect or voice changing going on during the cross fade and thus no glitches.
Crafty....
_________________________
John Allcock