I know nothing about singing bird mechanism, nor the substitute
material, but my question is, why mess with it?  The zephyr skin
I replaced with new in an Estey pneumatic organ (the key-scale
primary pneumatics in the console) was over 80-years-old when I
replaced it with new zephyr skin from Leather Supply House.  It
later had a problem of insect damage, caused, I believe, by an
outside door right next to the organ being open for an indeterminate
time in the fall, with damp and rainy weather included. This followed
a break-in at the church, and no one saw it for some time.  Some
insects seem to have caused small holes in a few of the pneumatics,
and correspondence convinced me that this is about the _only_ cause
for worry with this material.

Zephyr skin is thinner than note paper (.0015 to .0020 inch) but so
strong it's actually very difficult to tear by hand.  Make sure it's
not treated for softness or anything beyond its normal preparation,
and your usual glues should work.  I used fish glue and it did not
delaminate from the wood in the dampness, which fish glue can do --
indicating to me that the material itself resisted damp pretty well
and protected the glue.

I think both Leather Supply House and OSI [Organ Supply Industries]
have an acceptable quality product.  It's expensive but I wouldn't use
anything else for very small pneumatics that must be strong and tough,
and also easy to move.  The material I used had the look and almost the
feel of old-fashioned onion skin airmail paper -- until I tried without
success to tear a piece.

I wasn't there, but I'll bet that whoever complained that it actually
delaminated in layers of material, had two thicknesses of it and glued
it up by mistake -- it's that thin.

Good luck with your mechanical twitters 'n tweets...

Rick Hunter