Yes but the mixer volumes are saved inside the style?
It seems that all you can do is change expression.
Also, I dont this that you can do for Variation 1, ACC3
Guitar1 on MAJ and PIANO1 on MIN
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).