Greetings!  I would like to ask for some help from Duo-Art experts.
Before asking my question here is some background on the instrument
that I am restoring together with some of the conclusions that I have
been able to glean from drawings, service manuals and word of mouth
from  various l experts that I have been able to talk to.

The instrument is a 5' 6" Duo-Art Steck, serial #69884.  The Piano
Atlas gives a date of about 1922 which is clearly too early.  The stack
plays 80 notes (introduced in 1925).  The tracker bar floats and the
tracking ears protrude through the bar and the tracking mechanism acts
directly on the tracker bar (introduced in 1927?).  The tracker bar
tubing is routed outside the ends of the stack at the bass and treble
ends.  There are quick disconnects making it very easy to remove the
spool box assembly and get access to the piano action (introduced in
1930?).

The piano itself was manufactured before Aeolian made this last
modification to the player action.  The keys are cut out to accommodate
the tracker tubing and the holes in the keybed which allow this tubing
through have been filled in (in a way that makes me think that this was
done at the factory).  Also the key slip, which is screwed to the key
bed, is made from a piece of wood with cut outs (only visible when the
key slip is removed) for the dynamic and tempo controls.  All the
controls in this instrument are of course in the spool box.

There are signs that this piano was a cheap one since there is no
sostenuto mechanism.  Instead the centre pedal lifts the dampers in
the bass section only.  There is however a shifter.

One final point before my question.  The piano has been worked on in
the recent past and most of the tubing has been replaced.  I have
therefore no guarantee that the tubing is as Aeolian intended it.

Now to my question.  How is the Normal/Soft switch supposed to work?
In the soft position two lines are opened to atmosphere.  According to
the notes I made during dismantling, one of these went to the bass
connector block.  I assumed  (without verification, which was stupid)
that this simply went to the modulator box.  The other opened the level
2 (of 1248) line of the accompaniment dynamic control.

Imagine my surprise on opening the modulator box to find that there is
no modulator valve!  This box contains only the rewind cutout valve and
the regulator supplying vacuum to the dynamic valve box and various
control pneumatics.

It seems reasonable to suppose that the soft switch is meant to
operates either the hammer rail or the shifter pneumatic with hole 94
in the tracker bar controlling the other.  I can argue in favor of
either of these assignments.  This leaves open the question as to why
the minimum accompaniment level should be raised when playing in the
soft mode.

Can anyone help me?  I am nearly ready to reassemble having only the
stack to rebuild.

Regards

John Johns
Ottawa, Canada

P.S. Is there someone out there who knows the history of the
development of the Duo-Art system who has perhaps written about it,
or would be willing to do so?  For example, when was the electric
roll drive introduced, and when was the tracking device changed to
a system like the Standard?  Are the dates I have mentioned above
approximately right?  It seems that such information is needed if
one is to date a Duo-Art system with any accuracy.  Thanks, John