In my letter about this subject yesterday, I should have ended by
saying that the problem is definitely in the expression _system_, not
"box." I might have also clarified that the finding would be contingent
upon having eliminated any mechanical problems first, although at the
time, I was hoping that was understood.
Many of these questions could be isolated and corrected with a better
test roll. Duo-Arts are not like Ampicos, in that they are totally
non-compensating. They cannot compensate for anything, including the
number of notes played at any given time or a sluggish or leaky valve
that might affect other notes played with it or immediately after.
Therefore, the only way to regulate a Duo-Art is first, to use the
test roll, and then to play dozens and dozens of rolls through them
for several weeks and listen to hear little indications of things.
(Too bad no one has ever designed a proper test roll for these
instruments. The old Duo-Art tester #3 roll is so marginal it's almost
become a joke.)
Having received a personal E-mail from Mario, I began to realize that
his problem is really more basic than just the expression system.
I believe that Mario will have to "bite the bullet" and fully restore
his piano first. As it turned out, it doesn't matter how the note is
played, whether on accompaniment or theme they are still weak. Since
that could be just about anything, even including simple stuff like
trackerbar tubing dressed under the air motor and laying on the back
part of the keys, I suggested a proper and thorough check first, and if
something positive doesn't immediately come to light, then a complete
restoration is in order.
One other thing has also come to mind: When you notice that about a
dozen keys in the treble are weaker than the rest, it's human nature
to say, "the treble side is weak." It sometimes seems as though ALL
of the notes are weak, when actually it's just a few. Those same weak
notes may also be scattered over the treble compass, or they may all be
generally in the same area.
These are things that also give you clues as to what the problem could
be. On Steinways -- pianos with sliding repetition springs -- and
practically all other pianos as well, the problem sometimes is improper
action cleaning, stiff centers, incorrect parts replacement, and poor
(or no) regulation.
Sometimes it can even be the fact that the stack isn't precisely
located under the tails of the keys from end to end! You decide this
by using carpenter's chalk on the strikers and then seeing what the
striker line looks like from end to end. There are literally dozens
of reasons, these being a few obvious ones.
Reproducers of all brands are too often partially repaired and thought
to be "playing," until someone who wants them to perform as they were
intended buys it, hoping that the problem is minor and can be
repaired. There is no such thing as patching up a weak pneumatic
instrument perfectly. After all, everything in it is generally as old
as everything else! But once they are properly restored, and tested
out as perfect again, you can rely on them never to change on you or
quit playing because of elemental degradation or wear and tear in the
home environment for the next 50 years or so.
Pneumatics are the best medium I know of for playing a piano because
it is just as reliable as the piano mechanism itself, with the same
MTBF [Mean Time Between Failures] rate, and is inherently capable of
driving every note to its full limits of dynamic (both lowest and
highest) without loss of power or sensitivity, and without requiring
anything other than a player roll to do so. (Although the PowerRoll
is also a nice addition too, and is playing the Duo-Art at my web page,
as was mentioned earlier.)