Mike and David, thanks for correcting me about book music cardboard.
One of our subscribers plans to check on available North American
cardboard, just in case there is a new product which would be
equivalent to the good German material.

The question of spring stability still bothers me, and I need input
from an expert.  I _do_ know that the front compression springs on
my heavy Chevrolet sedan must be replaced every six years, when the
front license plate scrapes the curb!

I haven't seen return springs in the horseshoe chest magnet valves,
nor in the Concertola valve.  Were different styles produced,
perhaps for organ use?

The Stahnke electric valve only looks like a solenoid: the inner
steel core is fixed.  The only moving part is a tiny disk with a
"long" compression spring to assure fast return.

You say that a typical MIDI-operated valve has a low duty-cycle.
I disagree!  The soft pedal channel, and the lowest intensity
channels in a DuoArt, can remain "on" continuously for several
minutes.  The temperature of the valve assembly rises until it
stabilizes at a much higher temperature, as limited (typically) by
convection airflow.  At high temperatures the coil current is
reduced, which affects the turn-on time.  This is not a _big_
problem, but it must be considered in system design.  ALL these
little problems must be considered, and weighed to decide which is
the best overall valve design to purchase or construct. That's why I
plan to test as many different designs as I can find, and I'll
publish a report right here.

You stated "to date no one has been able to demonstrate that the
Reisner valve has any perceived inadequacies."  Well, the old
horseshoe style valve is _noisy_ : it clicks, loudly enough to be
annoying if it's not shrouded in a sound-muffling box.

On the other hand, I concede that different folks have different
"perceived inadequacies".  Few buyers of QRS and PlayRite music
rolls notice the sloppy timing in the rolls which are carelessly
copied -- and re-copied -- from old 1920s originals.  Because of
inconsistent and random response in the reader and perforator, the
slots in the roll don't match the original.  Chords which are
supposed to strike "squarely" instead "ripple" across the keys.
Maybe this inadequacy goes unperceived, but _I_ notice it, and
I consider the degradation objectionable.

When I questioned the practice, John Malone (PlayRite) answered
offhandedly, "Oh, that's all right, because we tell the customers it
was hand-played!"

Baloney!  If the chords in the original roll or disk file are "square",
I want them reproduced that way.  That will reassure me that
the critical timing of the expression channels is correct, too.

-- Robbie Rhodes