I've been vaguely aware of this for a long time, but
until last night I never looked at closely... You can arrange
for an instrument fader (or pan knob) to send a sysex
with one byte that contains the value of the fader.
Double-click on the fader's name and select the
"Assign Sysex" choice. What you do is type in the
definition of the entire sysex (including the F0 and F7)
in hex. A byte containing the letters "NN" is replaced
by the fader value, and a byte containing "VV" is
replaced by the number of the MIDI channel in use.
I used it in a song last night to vary the suboscillator
level and filter resonance on my Juno-106. (Yes, I
know it has sliders, but (1) they're kind of fragile, and
(2) I don't like to use the 106 as a master keyboard
because its MIDI implementation has some weirdities.)
I've got a request in the Feature Request forum related
to this...