To answer Randolph Herr's question about the length of the tracker bar
tubing affecting the player: your diagnosis sounds correct, finding the
repetition slower in the center portion of the piano.  It is most like-
ly due to the deterioration of the player system causing the pouches to
become porous, as someone has already pointed out.

The question is, What to do about it?  Short of restoring the mechan-
ism, there is a way to address the situation without a great deal of
work.  Select a slow note in the center of the piano.  Cut the tubing
off the ends of the nipples, both from the tracker bar and the valve.
When you cut the tubing off, leave a ring of the old tubing on the
nipple, but don't let it extend past the end of the nipple. This ring
is left on only to increase the diameter of the nipple.

Then, slide the next size tubing over the nipples, reconnecting the
tracker bar to the valve.  Run the test roll and see if the slow note
now repeats satisfactorily.  The larger diameter of tubing should make
the note respond correctly.  A length of tubing making a long run from
the tracker bar to a valve will cause resistance in the signal.  To cut
down on this resistance, it is not necessary to increase the size of
the tracker hole or to change the nipple size.  Simply moving up to the
next larger hose will eliminate the resistance.

Old players built before World War II were well-designed and will not
suffer from this problem, at least as far as the stacks are concerned;
nor will players in top condition.  However, increasing the diameter of
the tubing in the manner described comes in handy with some sustaining
pedal pneumatics and with homemade orchestrions.

Paul Manganaro