In 130520 MMDigest, "Building a Transparent Player Piano Action
Model", Joseph Osborne wrote:

> Now if you could only make the color of the air change with the
> vacuum level...

Just an idea: Put diffuse red/green LEDs into chambers that make each
such chamber "glow" red or green (or only red when "thin air" is in
the chamber), add some pressure-detecting switches somewhere out of
sight and control the LEDs with these...  Okay -- not something done
over a weekend...

In the same 130520 MMDigest, John A. Tuttle wrote:

> With regards to the internal workings of a player piano, just seeing
> that something 'does' work by no means helps explain 'why' it works.

That "why" is so elusive.  For long years, I have wanted to write
a book about "mechanical logic" (like clocks, railroad interlockings
from the past etc.) -- no pneumatics, no electricity, no such
"invisible" things involved.

Guess what: explaining some of the simplest mechanics is almost
impossible by just showing or building a model.  As an example,
the critical elements of Graham's escapement and the even simpler
version by Mannhardt are minimally curved surfaces, _not_ the visible
"big parts".

So the best explanation 'why it works' is actually a sequence of
annotated(!) diagrams or maybe an annotated(!) simulation plus(!)
some exploratory text (like "what would happen if this and that were
different? -- See, it would not work!"), but certainly not the thing
itself.

So, the goal of a transparent player action model, in my opinion,
cannot be "being an explanation", but "approaching an explanation"
-- having people ask "okay, now it gets interesting -- can anyone
tell me or show me how that thing works?"

This does work, as I find out when I open my crank organ, equipped
with some scrap paper (old organ rolls!) where I can happily explain
away what _really_ happens in there...!

Regards,
Harald Mueller

 [ Perhaps being able to view the moving parts will motivate the
 [ observer to read the placards or do the additional reading necessary
 [ to complete their understanding.   -- Jody