A search on the early D-A upright expression box turns up
little information on the 5-position switch labeled

  "Concert", "M P", "P P", "P Pedal", "Dance".

I was able to sketch some of the expression box connections of the
switch and may be able to puzzle out the rest once the expression
box is restored.  Attached is a picture of the box showing the extra
linkages with one of the two smaller pneumatics.  With the switch
indicator pointing at the "M P" level there is no change in the
mechanism whether set on the M or the P.  Also unexplained is
the double "P P" with the spacing in between the letters.  I have
a picture, if interested.

The old white cloth shown in the picture was still quite air-tight,
though replaced.  It was a light weight cloth with a black coating
on the interior surface.  The pictures shows an extra pneumatic which
lifts a lever that limits the throw of both accordions.  If anyone
has experience with this expression box, particularly opening it up,
I would like to hear from you.

Bill Chapman - in windy, dusty La Quinta, Calif.
shazam32@earthlink.net.geentroep [delete ".geentroep" to reply]

 [ Early expression box with extra controls
 [ http://www.mmdigest.com/Attachments/14/04/27/140427_105440_D-A%20expression%20box%20w%20pneumatic.jpg 

 [ Randolph Herr wrote about the 5-position modify switch at
 [ http://www.mmdigest.com/Archives/Digests/200205/2002.05.04.08.html 
 [ -- Robbie