In response to the question about the effect of the length of tracker
bar tubing, here is my understanding of it.

Obviously, the valve must have a bleed in order to exhaust air under
the pouch; it also has to exhaust the air in the tube leading to the
tracker bar.  With a small bleed, repetition can suffer if all this air
under the pouch takes too long to be vented.  But putting in a larger
bleed is not the answer, because then the problem is that, in soft
playing on low air pressure, the bleed "eats up" the signal, and there
is not enough air left to inflate the pouch and push the valve.

Obviously, if there were some Goldilocks "just right" size, the manu-
facturers would have used it; but there is not one right size.  You
either lose repetition with too small a bleed or get no soft playing
with too large a bleed.  This is why quality players have a double
valve system.

Clarence Hickman had a brilliant idea in using the vacuum that closes a
bellows and plays a note to also exhaust the air that is under the
pouch and in the tubing leading to the tracker bar.  His "ball bleed"
valve, used in the Model B Ampico, is the result.

Speaking of this "ball bleed," I want to ask a question: it seems to me
that it was not necessary to make this entire ball-bleed gizmo, when
all you need is a tiny flap valve, perhaps a quarter inch on each side,
made of pouch leather and put over the top of the hole where the ball
bleed went.  I would appreciate hearing from other readers on their
ideas as to whether this would work.

Randolph Herr