At a Musical Box Society Workshop in 1983, the late Alan Pier recommended
goat leather for band organ bellows.  The sample he passed around was
heavy but quite supple.  He cited two sources of supply:

   Pipecraft
   12 Hampden St.
   W. Springfield, MA 01089
   (PGL heavy)

   Kiefer Tanning Co.
   240 Front St. S.W.
   Grand Rapids, MI 49504

Please realize that this info is over 13 years old and these trails
may be cold.  You could also try these more recent references:

   Columbia Organ Leathers
   915 Lancaster Ave.
   Columbia, PA 17512
   800-423-7003
   717-684-4428 FAX

   The Leather Supply House
   412 W. Marion
   South Bend, IN 46601
   219-234-8990
   These folks have fish glue too. Good stuff.

Alan mentioned wetting the leather until moist (not soaking) to give it
more pliability in getting it to conform to its final shape.  He used a
wood block to force the leather onto the joints for better sealing.

There is a section on bellows covering in the book "Barrel Organ" by
Arthur Ord-Hume, 1978.

I have not personally done any of this type of work but merely pass
on these notes made way back then along with the more recent sources
for leather.

Please excuse this music box guy for venturing into the area of
pneumatics.  Truth be known, I have a strong fondness for the street
organs of the Netherlands.

Chuck Walker¶
Hopewell Junction, NY¶
cewalker@prodigy.com