It sounds like Dave Clark's problem may be in the transfer chest of his
Wurlitzer duplex roll frame.  The transfer chest contains the pouches
that determine by their position which of the two tracker bars is open
to read the roll.  I wouldn't try to solve any problem that far down
the line with a tracker bar pump -- or by blowing into the tracker bar
holes either -- except _very_ gently.  You don't want to do more damage
there than may already exist.

I realize this is not an explanation of how the duplex roll frame
works, either mechanically or pneumatically.  The duplex roll frame
is one fascinating and complex piece of equipment and a real workhorse
in doing what it is supposed to do day in and day out.  I know how it
works, but that is difficult to convey in words without diagrams.

Matthew Caulfield