In digest 95.11.29 Robbie Rhodes wrote, in part:

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Subject: Using Midi Editor for Adding Expression Coding

George Bogatko has introduced an interesting new subject 
(Re: Ampico-to-Midi in digest 951128).

But  Whoops!  Back up, George!  In digest 95.11.26 I was talking about 
transferring music data to Midi for archiving, etc., and all-of-a-sudden
you are talking about going the other way, from Midi performance into 
player piano commands.  That's a much harder problem, and I don't know 
of any automated method available right now to do it.

[Snip}

The "tracker-bar clamp-on" seems prone to leaking, which is _deadly_ on a 
reproducing piano.  A better method of hearing your editing progress 
would be with a set of "magnet valves" teed 
into the tracker-bar tubes under your Ampico piano.  Use a set of Reisner 
vacuum valves controlled by the equipment described by Mike Ames in digest 
951126. Be sure that the power supply (12 or 15 volts at 5 amperes) is 
well-filtered and regulated.  You don't want the valve timing corrupted
by hum or voltage sags due to crashing chords!

-- Robbie Rhodes

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I too have wrestled with the concept of a device which would
slip over the tracker bar and electronically replace the paper.  I even 
made some preliminary engineering drawings to accomplish this but have 
come to the conclusion that the most difficult nut to crack would be the 
fabrication of the gasket that would be needed between the tracker bar and 
its concave mating part.  The selection of materials for this would be 
critical in that it would need to have some slight compressibility (as 
in an elastomer) yet be rigid enough hold the extremely fine "web" width 
between holes.  My guess is that you could not do this with a die cut 
process as the force required to strip the material from the die would 
probably destroy the webs.  Perhaps a laser machining process would be 
more successful.  I believe the better approach would be similar to the 
CC-3 Cassette Converter manufactured in the '70's by "International 
Musical Industries", Santa Monica. [Come on Robbie, don't YOU know 
all about this?  Fill us in.]  My approach in my experimental system 
is to mount a bank of solenoid operated valves in a separate chassis 
(reversibly mounted) in front of or beneath a Duo-Art or Ampico stack, 
with a tube for each note or function connecting to a tee inserted 
into the hoses coming from the tracker bar.

Caution:  The following may SOUND like, but is not intended to
be, a commercial.  In trying to come up with a suitable solenoid 
operated valve for this purpose, I first looked at the direct electric 
magnet valves used extensively in the pipe organ industry.  While 
they are well suited for the function, they are fairly large, on 
the order of 5/8" x 1 7/8" x 2 1/4" for a small Riesner model I have.  
This is over 2 1/2 cubic inches before you add a valve seat and 
connector for the tubing.  Their biggest advantage is they are 
relatively inexpensive, a reflection of the quantities in which 
they are made.  I decided to make my own valve using a commercially 
available solenoid which is 3/8" square and about 1" long.  I add a 
valve seat and tubing connector for a total length of 1 7/8", giving 
a volume displacement of approximately .26 cubic inch, almost 1/10th 
the size of the pipe organ magnets.  Gang mounting the valves on a 
common aluminum rail (with necessary separation for cooling) increases 
the effective displacement to about .35 cu. in. per valve.  In an 
effort to buy materials and components in reasonably efficient 
quantities, I offered to sell these valves to others who might 
be interested in them for similar applications.  (Please see ad 
in July/August Amica Bulletin, p. 237.)  While several sets were 
sold, the overall response was, well, underwhelming.  Detecting 
that the interest may now be increasing, I am CONSIDERING "reopening 
the production line", again on a partially pre-paid subscription 
basis.  I am putting together an e-mailable package on this which 
should be ready in a few days.  If you are interested in receiving 
the detailed package, send me your email address with a request for 
it.  Since it will contain some bit-mapped image files (viewable with 
a Windows accessory), I will only send it to those requesting it as it 
may take several minutes to download.  I should be able to hold the 
maximum price at $8/valve but will probably not be able to get under 
$6/valve unless I get subscriptions for LARGE numbers.  As I am in 
the process of switching ISP's, please send requests 
to: ir004161@interramp.com   -John Grant