Robbie said:

 [ I'd sure like to have a special foot-pumped Themodist wherein the
 [ accompaniment level is always maintained at about 6 decibels down
 [ from the theme volume.  The normal Themodist has a fixed accomp
 [ level (set by the spring tension), and thus can't follow the
 [ pumping dynamics of the pianolist.  --  Robbie

Eh?  _Eh?  _EH??  If your piano is like this, it's a very rare beast
indeed.  I've only met one Aeolian-made Themodist instrument that had
a fixed accompaniment level -- although this is universal with Standard
"Solodant" actions, which is why rolls had to have SOLO and NORMAL
printed on them.

The usual Aeolian arrangement, ignoring the soft and sustaining pedal
levers, is to have two slider levers which are usually pressed leftwards
singly or together by the left thumb.

If you don't touch them, the instrument plays at a loudness proportional
to your pedalling strength.  If snakebites appear on the roll, there may
be a very slight accentuation, but usually there's none.

The levers (usually) operate knife valves which throttle the bass half
of the stack for the upper lever and the treble half for the lower
lever.  This enables you to bring out the treble or bass to taste.
The instrument is usually adjusted (I'm keeping away from words like
"should") so that when both levers are pushed hard over to the left,
a three-note chord in either half of the stack will just play, but a
four-note chord may fail.  The suction in these circumstances is
controlled by the two spring-loaded regulators for treble and bass,
which you adjust by turning the cylindrical adjusters threaded on the
springs.  The strength of pedalling, above a minimum, has no effect.

The one freak instrument I met was a push-up and it had pop valves
on the levers, so that this "hard-over" state was achieved as soon
as you pushed the levers any distance at all.  This conforms to your
description of Themodist.  But all normal Themodist instruments have the
knife valves, which enable you to subdue either treble or bass or both
in a graduated fashion, while "snakebitten" notes always stand out
according to the strength of pedalling (I assume that any THEMODIST
switch in the spoolbox is set to ON).  On these instruments, you can
achieve your 6 db differentiation simply by pushing the subdue levers
over (I will guess) a third of the way.

Hupfeld "Phonola" instruments have a similar arrangement, only with
one lever reversed in direction, so you squeeze the levers together to
get balanced theme.  (But the Hupfeld "Clavitist" cafe piano does play
ordinary theme rolls with accompaniment roughly at Duo-Art level 3 and
theme at DA level 8 !)

On some classical rolls you need far more than 6 db differentiation.
Rex Lawson got QRS to make a set of the Rachmaninov two-piano Suite
Op 17 and if you listen to two pianists playing the Romance, it's
impossible to achieve the same bold theme and silky accompaniment on
the roll without every last ounce of difference !

Dan Wilson, London

 [ I refer to the suction of the accompaniment regulator, which is fixed
 [ at a constant suction by the spring tension.  The slide valves can
 [ alter the air _flow_ to the stack, which helps matters somewhat, but
 [ I feel that a proportioned regulator would give better results,
 [ especially if the operator can adjust the theme-to-accompaniment
 [ loudness ratio during the performance.
 [ -- Robbie