DAN.,

VA-7 manual p171
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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.

on VA-keyboards

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):

for MAJ or MIN or 7 independently of each other, or for all 3.
for Example:

MAJ=MIN=7th
MIN=MAJ=7th
7th=MAJ=MIN
7th=MIN=MAJ

and you can also record the slider for style parts independently of each other.

for example:

for INTRO panpot from L to R and for VARIATION1 panpot from R to L.

and you can also record those sliders for each style tracks separately.

you can also set everything what you may think on MICROEDIT(midi events).
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very, very long ago done al this on VA-76.

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on microedit you can set even 2 drumkits on the same time as layer for example basdrum from kit1 and snare from kit2
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on Roland VA- keyboards when you record a style

for example on ACC3 track you can record if you like Guitar1 for intro but on ACC3 for varaion1 can record if you like Guitar2

or ACC3 for MAJ on intro1 Guitar1 but ACC3 for MIN on VARIATION1 Guitar2

another example:

intro1= drumkit1, Variation1=drumkit2, fill=drumkit3, Ending=drumkit4