Have you ever exercised a Duo-Art test roll on a Duo-Art reproducing
piano to check for proper playback performance?  Did you run into
difficulty trying to satisfy some of the requirements imprinted on
the roll or written on an accompanying instruction sheet?  Did you
ever wonder if you were using the appropriate test roll for the piano?
The information below (and some related inquiries) should give you
an idea why these questions arise.

During the years 1913 through 1938 Aeolian Corporation issued a
number of test rolls for their Duo-Art reproducing piano mechanism.
Historically, it is not clear precisely when the first Duo-Art
mechanism in a piano was sold, but 1913 seems about right.  Just when
the last Duo-Art system was sold is similarly clouded in the veils
of musical history, but 1938 is probably close.

Does anyone in the MMD community know how many different versions of
the Duo-Art test roll were released?  Were they all different?  After
the 'first' one (whichever one that was), did each 'new' one reflect
some pneumatic modification of the original Duo-Art system?  Presumably,
the Aeolian Corporation issued 'new' test rolls for a good reason.

I have managed to collect two distinct original Duo-Art test rolls
over the years.  They are the 1921 Electric Duo-Art Tester (S-2872)
and the 1927 Test Roll No. 3 (identifying number unknown).  Dave Saul
introduced me to the existence of the 1924(?) Duo-Art test roll
(S-3067) for electric and 'foot-blown' models.  These three test rolls
most likely reflect the oft-referred-to test rolls Nos. 1 (S-2872),
2 (S-3067), and 3 (no identifying number).

But did Aeolian release any other test rolls between 1913 and 1938?
Jeffrey Wood kindly looked through his Duo-Art piano roll collection
and found an original test roll that 'appears' to predate the No. 1
roll cited above.  He did not find an identifying number on his roll
but did report that the label on the box was printed in red ink, a
typical sign of an 'early' roll.

Unfortunately, the top portion of the box enclosing my S-2872 No. 1
Duo-Art Electric Tester roll was missing, so I could not check to see
if the ink used to print its box label was red or black.  The ink color
on the label of the roll S-2872 itself is not red or black, but
somewhere in between, perhaps light black or at least very dark red.

In all likelihood, a Duo-Art test roll was issued by Aeolian prior
to 1921.  This is based on the (reasonable?) assumption that a Duo-Art
test roll had to have been made available to the public when the piano
mechanism was first sold back in 1913.  Otherwise, there would have
been no 'convenient' way to ensure that a Duo-Art piano was playing
properly.  Maybe only the Aeolian Service Department and their service
representatives had such an early test roll.

The provenance of early Duo-Art test rolls is important for a
not-so-obvious reason.  That is, in order for the test to be musically
and technically sensible, the 'year of the roll' should closely match
the 'year of the piano'.  The concept of backward compatibility, so
common in today's computer software, may not have been applied by
Aeolian in the pre-computer era.

Although I have never seen or rebuilt an 'early' Duo-Art expression
box, I am told that they are physically quite different from their
'later' counterparts.  Aside from the fact that the Theme and
Accompaniment sections of the early Duo-Art expression box are
implemented in two disjoint sections, the knife-valve ports (holes)
inside them are circular in shape.  Does anyone know the diameter of
that circular porthole?

The circular porthole implementation contrasts sharply with the
'racetrack' shape (parallel sides with rounded ends) that one finds
in 'conventional' Duo-Art expression boxes within the 1916(?) to 1938
timeframe.  It is curious that the Duo-Art service manual, e.g., from
1927, still shows (in phantom view) the regulator knife valve portholes
in the expression box as circular, even though the racetrack shape
became standard about a decade earlier.  Interestingly, the porthole
shape for the modulator pneumatic (which also uses a knife valve) is
displayed with the racetrack shape in the same 1927 manual.

From a technical development point of view, it is worth mentioning
that in a "fan-accordion" expression box (1928 - 1938?), the shape
of the corresponding knife valve ports (realized as a rolling curtain
valve) is clearly rectangular (sometimes square).  From an engineering
perspective, the racetrack shape mentioned earlier is a good
approximation to the ideal rectangular configuration.

The shape of the knife valve port exerts significant influence on the
air flow regulation characteristics, especially when soft passages are
being reproduced on the piano.  The rectangular shape of the knife valve
port offers pressure regulation advantages over the circular shape, but
that is a subject for another article.

It turns out that the American Piano Company (Ampico) utilized the
"equivalent" of the rectangular shape in their air flow regulators from
the very beginning of their manufacturing operations.  However, to its
credit, Aeolian also utilized it, just somewhat later in the game
(maybe starting in 1915 or 1916?).  Hindsight shows that the Duo-Art
porthole shape evolved from circular to racetrack to rectangular at
Aeolian.  The Ampico B reproducing system utilized the rectangular
porthole (or equivalent) shape almost everywhere in their air flow
regulating mechanisms.

Assuming that what I have presented here is correct, it should not be
surprising that there might be difficulties in satisfying the different
playing tests called for on the Duo-Art test roll.  After all, the
tests are only fair when the year of the roll closely matches the year
of the piano (Duo-Art reproducing mechanism).  It may be that we have
been mismatching our test rolls with our pianos.  Hopefully, others in
the MMD community can shed more light on this subject.

Does anyone in the MMD community have original test rolls other than
the ones described above?  What are their identifying numbers?  Can you
assign original Aeolian identifying numbers to the two rolls cited
above, for which none have been found on extant samples?

Do you have additional information regarding why Aeolian chose to issue
the test rolls that they did?  What differences, if any, exist on the
four test rolls described here?  Are there British counterparts to the
American Duo-Art test rolls?  Do the 'corresponding' British and
American Duo-Art test rolls match?

Please share your knowledge and experience with us.  Any input relating
to the above questions is welcomed.

Bill Koenigsberg
Concord, Massachusetts
billkberg@comcast.net.geentroep [delete ".geentroep" to reply]