Was it just me, or did others think Ed Gloeggler's description (MMD
98.02.15) had reversed the terms theme and accompaniment in the first
bit of his description?  A pedal Duo-Art uses the original pedalled
suction level for theme, and throttles it down for the (quieter)
accompaniment.  If Ed's machine is really the other way 'round, then
(apart from not understanding how it can work), it sounds interesting.

The pedal Duo-Art is, when stripped of its mystique, nothing more than a
perfectly ordinary Themodist system with the accompaniment level made
variable by adding an accordion pneumatic.  Often these systems have a
'crash' system like that described by Spencer Chase, where reaching
level 15 (or lower) opens a pallet valve which switches both treble and
bass to theme, so bypassing the regulator.

Robbie, the pedal Duo-Art offers in part the control you said you want,
doesn't it?  Why not try one of these, and create a link to operate
knife-valve yourself.  With hands in use for the levers, perhaps a knee-
swell would be the thing!  The Hupfeld Solophonola offered a variable
accompaniment level, I believe, with theming permanently on and the
operator altering the degree of accompaniment attenuation with a lever
on the keyslip.

In my experience, how well a Themodist system regulates the
accompaniment level can be quite variable.  Some machines hold a fairly
constant level irrespective of pedalling, while with others the level
rises as you pedal harder.  The operator should be able to float the
level using the theme levers, anyway.  Inside the expression box, the
theme sliders are shaped with a notched end to give a gradual cutoff
effect, altering the relative balance of regulated and unregulated
suction supply to the stack.

Coupled with an ability to pedal the accents you want, a Themodist
system offers a pretty decent amount of musical control.  I know some
contributors have said the sliders don't have any real control effect,
but that's not my experience at all.  Controllability does vary widely
between instruments, though, and you have to get to grips with what a
particular instrument is capable of.

A couple of incidental thoughts: Dan Wilson refers to two spring-loaded
accompaniment regulators, for bass and treble.  Aeolian instruments
usually only have one regulator for the whole stack, although themed
Standard actions I have seen have separate regulators.

Regarding Peter Coggins' home conversion of a half- to a full-Duo-Art,
original Aeolian Pedal-Electric Duo-Arts have a sprung-loaded cutoff
slider which automatically isolates the theme side of the box when
pedalling.  As a result, even if you switch the machine to 'Duo-Art'
position, you aren't powering the complete box, just the accompaniment
side.  One of the effects of this cutoff is to isolate the spill valve
when pedalling.  Whatever the thinking behind it, it is clear that
Aeolian didn't expect anyone to pedal a full Duo-Art.  Probably the word
'why?' was hovering in their minds!

 [ "Why?"  Because some music rolls have poor coding, and energetic
 [ pianolists want to create their own interpretation!  :-)  -- Robbie

Julian Dyer

 [ I don't like throttling the air flow for expression control.  The
 [ Art-Echo reproducer used it, and the rolls are devilishly difficult
 [ to code because there is so much "droop" in suction as more
 [ notes are struck.  I favour the pressure-regulated designs used
 [ by Welte, Hupfeld and Ampico.
 [
 [ The proportional regulator which I envision will, I hope, reduce
 [ the "lever wiggling" because the accompaniment pressure will
 [ follow the (pedalled) theme accents.  Richard Vance is designing
 [ an external modification of the Themodist accomp regulator for this
 [ purpose, and I think it might also be accomplished easily using a
 [ curtain regulator scheme adapted from the B Ampico.
 [
 [ How can I measure the flow characteristics (the "controllability")
 [ of the slide valve on my Themodist, for comparison with a known
 [ "good" unit?  -- Robbie