I have a question for this august group concerning bleeds used in
pneumatic systems.  I have seen the term "vents" used also.

Vacuum operated systems use a bleed to return pouches and valves to
their original state after the atmospheric signal from the roll has
ceased.  Well and good.

Now, in a pressure operated system bleeds are also used for the same
purpose.  Tubular pneumatic pipe organs used bleeds which were usually
holes drilled in the lead tubing coming from the pipe chest to the
console.  The tube with the holes ran through a pressurized box.

That being said, my question is this:  Why are adjustable bleeds
necessary on busker organs?  Why not a fixed bleed?  After all,
we are not talking about long tubing runs.

I am sure a number of you have the answer.  I don't.

Ed Gaida
16 blocks north of the Alamo in San Antonio, Texas

 [ An adjustable bleed was typically a needle valve: a tapered air port
 [ with a machine screw ground to a matching taper.  It was convenient
 [ for testing but it gathered dust quickly, and so when the mechanism
 [ reached production the tapered valve was replaced with a simple
 [ aperture bleed.  The Ampico B service manual shows needle valves
 [ in the pedal compensating device but a fixed bleed is found in most
 [ production units.  -- Robbie