Hello,  Randy Hayno asks about the operation of his pedal-only "Half
Duo-Art" [200712 MMDigest].  This action was used extensively by The
Aeolian Company Ltd., London, in almost all of the instruments that it
sold -- even in the Steinway Model O grands.  It enabled the Company
to increase its sales of Duo-Art music-rolls, which was a lucrative
line of business.

If restored and adjusted carefully, the action is capable of quite
satisfactory results, especially if the Pianolist learns to read
and interpret the Theme coding of the Duo-Art rolls and to pedal
accordingly.  The Accompaniment coding is read and applied by the
action itself, as are the sustain and half-blow pedal perforations.

The Aeolian Company manufactured two slightly different expression
boxes and associated controls.  The simpler one requires the Pianolist
to hold the Treble and Bass graduated expression levers fully over to
the left when playing a Duo-Art roll, thereby directing the stack
suction through the regulator.

Theme notes bypass the regulator as in a conventional Themodist
Pianola, but the Accompaniment is controlled by the Duo-Art accordion
which sets the position of the regulator knife-valve.  To relieve the
Pianolist of the need to hold the levers across -- and possibly fail
to do so consistently -- a small brass catch was provided to keep the
levers in the correct position.

The second and more sophisticated system removes the need to hold the
levers over (as per the electric or pedal/electric full Duo-Art).  When
the spoolbox selector switch is turned to the Duo-Art Rolls Automatic
Control position, a pair of valves identical to the Theme secondary
valves operate to close off the graduated expression ports.

Depending on the age of the instrument, this is achieved either by
a primary valve block which takes its signal from the spoolbox switch
(in the case of a single metal switch), or by a vacuum or atmosphere
output from the spoolbox switch (in the case of the earlier double
wooden switch).

It is very likely that Randy's instrument is either tubed-up wrongly
or there is a split tube, and I would venture to suggest that his
instrument is fitted with the second type of expression box.  He
mentions that the piano is a German (Gotha) Steck.  These were not
produced after the early 1920's, so it may well be that the earlier
double switch is fitted.

There were also different means of actuating the Duo-Art accordion,
either by a cut-out in the accordion valve-box or by a cut-out mounted
next to, and to the rear of, the spoolbox (sometimes incorporating a
cut-out for notes 1-4, and another one may be fitted on the other side
of the spoolbox for notes 85-88).

There are many subtle variations of layout and system to be found in
Aeolian's instruments, so the above should be taken as a basic guide
only.

Kind regards,
Mike Boyd
Rye, UK