What is a Themodist?

Subject: What is a Themodist

Reyah Carlson asked (981107 MMDigest):

> Could somebody tell me what, and where the Themodist is located,
> or at least what it looks like, in my piano?  I was told it has
> one, I am not sure exactly what its function is, and where it is
> located...  I do know that on some player rolls, the small holes
> to the left and right edges (also refereed to as snake bites)
> trigger the mechanism.

Themodist is an additional gismo that is integrated almost invisibly
with the treble and bass subduing knife valve arrangements.  Additional
valves are provided inside the two chambers which when actuated by the
appropriate "snakebite" perforation, "short-circuit" the choke effect
of the hand-worked knife valve which is subduing (choking the suction)
on that half of the stack.

These automatic valves are driven from two primary valves which
are usually housed in a small additional box mounted on the stack.
Sometimes where four-hole tracking is provided the valves for that
are housed in the same box, and also the auto sustain (and sometimes,
hammer-lift) primary as well, so the box can get quite complex.  If
a THEMODIST ON/OFF switch is provided in the spoolbox, it controls
suction to the Themodist primaries -- but quite a lot of instruments
never had this and with these, "Themodist" is armed at all times.

The sign of a perfectly working Themodist instrument is firstly that
the two subduing levers do their job properly.  The upper sliding lever
in the pair second from the left on the key-slip normally subdues the
bass power (so is most often used) and the lower the treble.  Sometimes
they get switched over in ignorance in rebuilds, but I've found I can
adjust to that quite quickly.

If both levers are held hard over to the left, the instrument (pushup
or piano) should just speak, quite softly, with hard pedalling and
three-note chords on either side of the keyboard (divide at E/F on
Pianolas, E-flat/E on pedal Duo-Arts); and reliably speak with two-note
chords.  The 88-note test roll playing in thirds is quite a good test
for this -- the power of strike, with levers hard over, should not
change when the scales cross the divide.

The amount of subduing is a matter of taste and while I like it really
savage so the piano almost fails, I know professional players who
don't.  It can be adjusted, if the knife valves are positioned
correctly and not leaking, on the treble and bass regulator springs
(these are the pneumatics which provide compensation for large/small

Now some snakebites come along on the roll and we must assume they've
been cut in the right place and aren't ahead of, or behind, where
they're normally placed, which is starting about 1/32 inch or 0.8 mm
before the "theme" note they relate to.  (Advancing or retarding
snakebite positions slightly is sometimes done to emphasise certain
notes in a chord, but this will be rare.)

If you are pedalling hard with the levers hard over, on a good
instrument the "theme" notes will play really loudly while the
accompaniment remains soft.  There is sometimes a small amount
of carry-over of this sudden burst of power into the accompaniment.

In late instruments this will be such a marked effect that the pedals
under the feet actually tremble and give you a tickle.  In earlier ones
where the valve proportions weren't so well worked out, there is still
a "theme" effect but it is weaker and the "pianolist" must assist the
effect with appropriate accents given with the feet, just as he or she
must do entirely with non-themed rolls.

"Themodist" (without the name) is also the basis of the Duo-Art repro-
ducing system, where instead of hands and feet the accompaniment and
theme accordions control the two almost instantaneous playing powers.
Pedal-worked Duo-Arts are a special case, being a hybrid of true
Duo-Art and Pianola, on which I withhold comment since I've never
worked on one.

If Aeolian had their time again I daresay they would have thought
of a system which accentuated notes without having to delay or advance
them relative to the accompaniment, but as it was, "Themodist" was
a very creditable second-best.  It makes playing romantic music, in
particular, very convincing and pleasant.

In Europe "theme" system pianos were the norm and the majority of
classical rolls and even a lot of the 1930s dance rolls are "themed"
(= "themodised" = "accentuated").  Under I think the 1909 Buffalo
Convention rather than the 1908 one (someone can do the research
and correct me) all the European firms making 88n rolls used the same
standard, except that the Hupfeld sustaining pedal port is about
0.1 inch (2.5 mm) to the right of the American standard position,
because they were trying to fit four Triphonola dynamic tracks in
with it to the right of the bass theme port as well !

The ultimate test roll for Themodist should strictly check the speed
of the Themodist valves by repeating a chord while snakebites are swept
past its start, from too late to too early.  Alas, I've never seen such
a roll.  Themodist test rolls always have the snakebites in the right
place !  There should at least be as much "theme" playing in the bass
as in the treble, and Aeolian's British 88n test roll provides this at
the end.

My favourite piece for this, though, with which as "independent asses-
sor" I used to pass or fail Mary Belton's rebuilds of Themodist instru-
ments in her Brighton shop in the early 1970s, is the last-but-one
Etude Symphonique Op 13 by Robert Schumann, which requires silky soft
accompaniment in the left hand with an increasingly prominent theme in
the right.  If this piece can be played convincingly without having to
provide foot accents, the piano is ready for a long and satisfactory
life !

Dan Wilson, London

This article, which appeared in the Mechanical Music Digest on November 8, 1998, has been reprinted here with the express permission of the author and the owner/editor of the MMD.
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