All evidence so far suggests the Duo-Art was first offered to the public in the New York Sun newspaper on Sunday 1 March 1914:

  "The Aeolian Company, originators and sole manufacturers of the
  Pianola, take unusual pleasure in presenting a new and wonderful
  development of that instrument, The Duo-Art Pianola."

It seems to have been a fairly hasty debut, only Steinway Duo-Art uprights being available for some time.

Instruments with earlier serial numbers do not belie this date; a list of all Hamburg Steinways ever supplied to UK Aeolian shows that numbered instruments with enlarged cases were manufactured and shipped to London in batches for equipping with the Pianola.  Grands received Aeolian-made lids, legs, pedal-boxes, lyres and valances and elongated NY Steinway piano actions.

Pianos were not finished and despatched to the showrooms until months later, and the same was probably true for New York Steinways, so that late 1912 instruments, for instance, may not have appeared for sale until 1914 and 1928 models until 1930.

Duo-Art pianos were not produced in the UK before 1919.  Just a few must have been imported from the US in 1914 before the start of WW1.  The earliest known is an electric-only 1914 New York Steinway Style O grand with separate steamboat pump in a box, which may have been a demonstrator.  It has the Temponamic lever, a big 88-note cross-valve stack, and an inverted US expression box with worm and locknut zero adjusters, a separate Themodist secondary valve box and no modulator.

The expression box regulator pneumatics are slightly smaller than later examples.  Theme and Accompaniment regulators must always have been unified in all normal Duo-Arts to allow the common spill valve function intrinsic to the expression coding.

From 1919, UK Aeolian installed their own design of electric-only Duo-Art expression boxes with a separate Themodist secondary valve box.  Grand boxes have the regulator pneumatics on top, in uprights they hang down below the key bed.  Then, from about 1923, because UK patrons wanted still to be able to pedal and interpret Themodist rolls, the majority of instruments produced were pedal-electric, with a more complex expression box common to both uprights and grands.  Perhaps these are found in the few US pedal-electric pianos.

All UK boxes use double-screw t-bar zero adjusters.  Being somewhat purist, they mostly used same-strength regulator springs and never had the crash valve that US Aeolian's Creary Woods so deprecated.  UK instruments commonly have suction unloaders to set the pump supply tension, but modulators were never fitted.  The majority of UK expression boxes have the normal round knife-valve ports, but some late models have the same elongated ports as late US instruments, almost certainly to make pianissimo repetition more certain.

No UK-made instruments have been found with the later fan accordion expression boxes.  These Welte-type designs bear all the fingerprints of the ingenious Tolbert Cheek, and must have been produced royalty-free by Aeolian after it acquired all Welte and Auto-Pneumatic assets in 1930.  Several US instruments I've examined with these expression boxes include strategies to retain the Theme-modulated Duo-Art spill function.

An original UK development probably from the early 1930s was a unique Angelus-Artrio-type Duo-Art expression box in a Steinway O at London's Musical Museum.

Based on the unequalled Themodist and with its interlaced double 4-bit digital control and Theme-modulated spill valve giving 87 selectable levels, the Duo-Art is much more sophisticated and capable than most appreciate.  So far as is known the Duo-Art is the first ever application of binary digital coding to machine control, and its accordions are the first ever physical digital-to-analogue converters.  It was the most consistent of all the reproducing systems, a tribute to its essential rightness of concept.  A succinct account of its history and function appear in our Player Piano Group centenary book, "The London Duo-Art Pianists."

Two extraordinary minds turn out to be mainly behind the Duo-Art: African-American Joseph Hunter Dickinson, for many years Superintendent of the Aeolian Company's Experimental Department at Garwood, New Jersey, and Francis Lincoln Young, of Aeolian's Invention and Research Department, as revealed comprehensively by Rex Lawson in the UK Pianola Institute's Pianola Journal No. 24, 2014.  Dickinson's many patents provide hours of surprising revelations.

Patrick Handscombe
Wivenhoe, Essex, UK