Hi All,  The best and most accurate plans available today for
building Wurlitzer unit valves is by Bob Humes.  If you want to
approach and build the unit blocks just like the originals, the only
thing I would change is I personally use zephyr skin for the pouches.
They are very thin for a quick response time and are air tight.

You might hear people mention that insects are attracted to zephyr
skin but is false.  If this was the case, insects would be attracted
to any leather.  You must use a soft flexible zephyr skin.  I purchase
mine from the Leather Supply House.  If you purchase it from a place
like the Organ Supply House it would be to stiff and would not work.

Another misconception is that zephyr skin shrinks or stiffens up.
Today zephyr skin is make differently than 100 years ago.  It worked
fine on the originals and will even work better today.  I build
hundreds of these at a time and have yet had a customer return a valve
for a faulty pouch.  Hope this helps you to build a quality Wurlitzer
valve.

Musically, Robert Loeffler - Roberts Musical Restorations
Deland, Florida
www.robertsmusicalrestorations.com