on my post this part is from manual:


DAN.,

VA-7 manual p171
------------------------
Expression (control change CC11) is a subsidiary volume
message that works relative to the volume (control
change CC07) message. Whenever you set
Expression to �127� the resulting part volume will be
equal to the value specified for Volume (CC07).
The Volume values of the Arranger parts can be set in
Mixer (see page 112) mode.

--------------------------------

other things you can read are just possibilities of Roland VA-series for styles and are all tested very very long time ago.

again:

you have inside style creator a mixerscreen for:
Expression, Panpot, Reverb, Chorus

you can even record the sliders when you move them(like motorized faders).

and yes they can be saved inside the style on VA-serie and i think you can do even more on G70 and E80.

on Roland MicroEdit you can do many things, So about your example of Guitar and Piano is certainly possible.

unfortunately I still have a persoanal zip disk but no zip drive (no longer Roland VA-76 any more for very very long time now, otherwise you could see examples).