In a letter of 7 May, 1923, W Creary Woods wrote from Aeolian,
New York, to Reginald Reynolds in London:

  "There has not been any radical change in any of our instruments,
  especially the Weber and Steinway pianos.  In the small Aeolian
  Grand and one of the cheaper Uprights there was a change made in
  the pneumatic action.  Instead of using graduated pneumatics as we
  have in the Weber and Steinway, they used the same size pneumatic
  throughout the piano.  Of course, this means some effect upon the
  music.  The bass will not play as loud as on the Weber and the
  treble may play a little more brilliantly, but inasmuch as the
  piano itself has not the power, the results are not bad.  There
  was some talk about using the same size pneumatics on all of our
  instruments, but I am very much against it as it would make a very
  material change in all our records."

We know from UK Aeolian employees that action pneumatics made by
out-workers were graded at the factory, presumably for the closing
resistance caused by varying hinge tightness, probably using some kind
of hand-held spring device.

The factory also possessed test benches for setting up pneumatic
components and doubtless whole stacks, especially for the more expensive
instruments.

A look at an original unrestored Duo-Art stack reveals that the open
spans of the pneumatics are set differently for the three decks, by
means of different thickness felt on the support rails, to compensate
for the different weight of the metal pushrods.  The middle and top
decks are set about 1/8" and 1/4" less open, respectively, if I
remember correctly.

Many of the pneumatics have hinge springs, and I believe these were set
up to give a constant starting force throughout each section.  There's
a knack to pulling out one end of a spring, twisting it and pushing it
back into the hole.

Because of this and different initial volumes of the pneumatics it
seems that he valve travels were set differently in the different
sections on the best instruments.  The key is to just allow each
pneumatic to open at maximum speed with minimum resistance for best
repetition.

I don't think Aeolian UK ever adopted the idea of tweaking the starting
span of each pneumatic to compensate for action differences like Ampico;
I've never come across it on unrestored actions.  It doubtless makes for
super evenness if you've the patience, but doesn't seem to last too long.
Better I think to achieve a consistent stack and if necessary tweak the
piano action and voicing.

When a stack is regulated in this way the reducing hammer weight in
each section confers a slightly higher dynamic increasing with pitch
which allows the Theme to sing out clearly even at small differences
between Theme and Accompaniment.

Patrick Handscombe
Wivenhoe, Essex, UK