I have a generic no-name orchestrion that plays style "O" rolls.
It appears that holes #15 & #16 (Drum Expression Off-cancel & Drum
Expression On-Cancel) control expression for the entire machine,
not just the drums.  They control an expression regulator that is
hooked up to the main vacuum line of the orchestrion.

Is that right?  If that is correct, why do they call those holes
"drum expression"?

A second question is on the "Swell", hole #87 in the tracker bar.
My swell regulator is also hooked up to the main vacuum line of the
orchestrion.  What exactly is swell supposed to do and regulate?
And should it be hooked up to the main line?

I have Craig Brougher's book, but that particular chapter confused
me a little more than it helped me, with all the different types of
expression used, etc.,

Thanks for your help for this newbie!

Charlie Morgan

 [ Charlie's questions concern two distinctly different topics:
 [ (1) What use of the controls did the music roll arranger intend,
 [ and (2) how should they be connected in Charlie's instrument
 [ (which might be quite different from the instrument that the
 [ "O" roll was arranged for)?  -- Robbie