Notes repeating on bridges are because the valve is dropping and
re-opening. The problem is always caused by more air being removed
from under the pouch than is being admitted.

The reasons for this have been discussed. Natural degradation will
see pouches getting leakier with age -- and more leakage through the
wood -- in every player ever made. Dirt will reduce flow through
bleeds, hence tracker bar pumps. Ill considered changes to bleed
size can affect the overall system balance.

I spent a lot of time recently on my Aeolian double-valve Pianola
action, with some interesting results. I installed new valve faces
and pouches using Columbia Organ Leather's "sealed" Tan Pneumatic
Leather (CTL).

Initially I found some notes behaved strangely, hard to describe but
clearly not doing what my pedalling intended. The dynamics didn't
respond as I expected. I next reduced the primary travel to what was
probably originally intended, 0.025". And found that the notes were
repeating on bridges. The lower travel allowed the valve to complete
a cycle across a bridge.

With larger travel you can infer that the valve partly closed, and
hence interrupted the operation of the secondary, thereby meaning
the pneumatic wasn't closing smoothly according to suction but was
stuttering. Which explained why the dynamics weren't responding as
expected.

Generalising this, you can see that any player where a note repeats
under low paper speed will have interrupted operation at higher speeds.
If the notes repeat at ANY paper speed, the player will not work
properly at any other speed! This choking effect will definitely affect
playing, and I suspect is a fairly common cause of poor performance,
invisible within the system and rarely if ever discussed.

Clearly the cause of all this in my case was the new pouch leather.
So, I sealed it using the traditional rubber solution, which is natural
latex dissolved in naphtha (search for 'rubber solution' rather than
by any maker's brand name --- this is a natural product). Regardless of
what has been done to CTL, it still needs further sealing for player
actions. Other friends have found this out as well.

We know that Ampico said publically that they sealed pouches, but
I expect everybody else did as well. A friend who spoke to original
Aeolian workers was told they rubberised all pouches. My conclusion
from this is that it's quite acceptable to re-seal original pouches
if in good flexible condition, as many are. Over the years I've used
things like neatsfoot oil that sink into the leather fibres but this
doesn't last. So, rubber solution is my latest go-to.

When the 88-note roll standard was agreed in 1908 it specified the
minimum size of roll perforation, but said nothing (as far I have been
able to find) about the size of chaining bridges in notes. In 1908 it
was not normal production practise to use chaining so perhaps it just
didn't get considered.

Julian Dyer