This is a good time to explain for newbies and oldies who may not
have figured out everything about how player system valves work to go
through this giving my terminology to answer John Tuttle's question.
In player system valves there are several valve types and I will try
to explain the terminology I and some others use.

General terminology: there two main types of valves, Primary and
Secondary.  A Primary valve simply opens a hole larger than the one
in the tracker bar to activate the secondary valve.  This was done
to speed up repetition on the earliest systems that used heavy large
secondary valves.  Their terminology can be "exterior type valve"
because the valve seat is totally on the outside of the chest, while
the secondary valves have all the valve surfaces on the inside of the
chest so they may be called "interior type valve."

The leather involved in a valve will be called the "valve facing,"
while the hole that leather closes or seals off will be called the
"valve seat" because the valve facing sits on that hole which may or
may not have a brass or Bakelite surface around the hole for the
leather to sit on.

Primary valves are usually button valves -- leather on the bottom
side of the button -- with a closed outside valve.  They sit oriented
to move up and down when activated, so the external valve seat will be
on the top while the pouch pushes on the button inside and that would
be the valve facing on the bottom that seals upon activation.

This would be the definition of a poppet which is a dowel pushed from
the bottom and moving in a guide hole which is the hole through the
primary chest.  (That channel serves dual purpose as the hole under
the top button and also leading to the secondary pouch.)

In a single valve system, or in the secondaries of a double valve
system, many of those valves move up and down with the orientation of
how the valve sits when operating.  There is a valve facing near the
pouch that when closed keeps the high pressure of the valve chest from
leaking atmosphere into the chest.

In Simplex, Wurlitzer valve blocks, Ampico, Duo-Art and others the
valves move up and down.  That inside valve can be called the bottom
or inside (valve) seat.  The other end of the valve stem has the valve
seat that is surrounded by the atmosphere when at rest.  When the valve
activates that open valve seals closed, allowing the chest pressure to
surround that valve and that activates the pneumatic to play a note or
push a pedal.

So primary valves are small exterior button valves that sit on the top
of the chest sealing the hole in the chest that leads to the pouch of
the secondary valve.  When activated the bottom seat closes and the top
seat is opened to allow a gush of atmosphere into the pouch operating
the secondary valve

Secondary valves are interior valves with facings on the outside of
the valve disks.  The bottom or inside or pouch side valve is leather
on a fiber or wooden disc.  (If it is wood it looks like a "biscuit",
in the southern USA use of the term, so I often call the wooden slice
of dowel a biscuit, but some may not use that term.)  Secondary valves
close the bottom or inside valve while the top or outside or atmosphere
valve seat is open,  When activated the top seat is closed by the valve
while the bottom or pouch side valve is pushed open by the pouch
activating the pneumatic.

Secondary valves are able to be positioned so their travel is front
to back in many player systems instead of the up and down of those
systems mentioned above.  This is a 90-degree shift in orientation.
They have valve guides to hold them in place so they can be positioned
that way and still seal, while primaries are seldom seen in any
position but up and down.

One other thing:  The only difference between the secondary valve of
a double valve system and a single valve in a single valve system which
has no primary valve chest is the bleed.  The single valve system uses
what may look exactly like the secondaries described above.  Instead
of a primary valve to suck the pouch back down after activation, it
uses a bleed cup with a hole often in the #60-#71 drill size which is
much smaller than the size of the hole in the tracker bar.

As I said, the early systems before the mid-'teens (somewhere around
1915) may have been large and heavy.  These needed the huge gush of
suction to pull the pouch down in the secondary valve and an equally
large gush into the pouch to activate the pouch.

In later versions of the pneumatic player system the valves got smaller
and smaller as designers figured out ways to make valves lighter and
smaller and faster and still get sufficient air in and out of the
pneumatics that play the notes.  All these system are able to repeat
at the barely believable rate of about 10 times per second in the best
systems.

Doug L. Bullock - Piano World Enterprises
Alton, Illinois
http://www.facebook.com/PianoWorldEnterprises/ 
http://www.thepianoworld.com/