On 17 Nov 2010 at 7:52, John Phillips wrote:

> I think I've got the story right, but I'd be very pleased to hear
> from any other Half Duo-Art owners.

Hello John,  I'm not sure that any of the answers so far really match
the question, so here's how it works on mine.

The piano is a Steck half-Duo-Art, Style 323P, S/N 65255, which Pierce
Piano Atlas puts at around 1921.  As discussed previously, it has the
same 3-position control in the spoolbox as yours.  It has the usual bass
and treble subduing levers spring-loaded to the right (loud) position,
and no Temponamic knob.

Now, with the Duo-Art switch set to OFF (the rear position), the piano
plays all 88 notes.  The Theme holes and valves operate, but only have
an audible effect when the subduing levers are moved some or all of the
way to the left.  The second step of the knife valve accordion is
permanently activated to set a minimum playing level.  This position is
used for regular 88-note _and_ Themodist rolls.

In the front position (Duo-Art ON), the 8-way cutout block is activated
to kill the four notes at each end of the keyboard, and to direct the
four accompaniment level holes to the accordion.  The bias on the
second step of the knife valve accordion is removed.  The subduing
levers are moved fully to the left and held in place by a hinged
latching lever.  This setting is used for Duo-Art rolls, where the
Accompaniment level is controlled automatically by the accordion, and
the Theme level is controlled manually by the skill of the pedalling.

In the centre position with the small arrow, the top and bottom four
notes remain disabled, but the accompaniment level holes go nowhere.
The knife valve accordion is set permanently at the second step, and
the subduing levers and theme valves operate exactly the same as in
position 1.  This setting allows a Duo-Art roll to be played with
manual rather than automatic expression, as if it was just a normal
Themodist roll.

That's how it works on mine, but there's no guarantee that Aeolian ever
built two the same!

Best regards,
John Wolff
Melbourne, Australia
http://www.vicnet.net.au/~wolff