I did a simple experiment with my old pumper which entertained me
mightily as a teenager.  I had wondered why/how the tubes between the
tracker bar and the action stack could be of quite different length
yet perforations on a roll crossing the bar at the same time would
sound the notes at the same time.  So I took a short piece of tubing
and a coil of tubing approximately 30 feet long and plugged them in to
a couple of stack nipples.  Opening and closing the other ends of the
two tubes would, of course, sound the notes; the entertaining part was
that opening and closing the tube ends simultaneously would (appear to
me to) sound the notes simultaneously!  The notes would repeat about
as well, too.

Five decades on, I still don't understand how that could be.  Surely
the bleed has to reduce the pressure in the entire length of tubing.
Surely there is drag associated with moving the air in the tubing.
I had thought then that the volume of air that it took to allow the
pouch to rise would be made available by a vacuum pulse traveling down
the tube, rather like sound or the resonance between cylinder and
exhaust volumes used in the design of internal combustion engines to
more efficiently and quickly exhaust gasses.

Douglas Heckrotte
Philadelphia, Pennsylvania