While I agree with Doug Henderson that the Smithsonian exhibit should
have showcased more pneumatic players, a lot of us are interested in
the more modern piano actions.  Here's a technical description of the
original Pianocorder, which I just found in a 1977 clipping from
Electronic Design, one of those free magazines sent to engineers.
I saved interesting articles like this when I worked for Bell Labs.

There's some major information here on the tape format, the use of
pulse-width expression control to the solenoids (which allows small,
cool output transistors), and most of all, the obvious but ingenious
technique for recording hand-played expression.  After all the
arguments about whether any of the reproducing roll studios actually
recorded the pianist's expression, Welte or otherwise, this is a
refreshing addition to the lore!

I've scanned the text and quoted it below.  Also I'm sending separately
the black and white photo, which I hope Robbie will place in the
picture gallery.  Note that it was taken by SCUBA divers on the S. S.
Poseidon -- or perhaps the magazine editor goofed.  Yes, it was printed
upside down, which I fixed!  Look closely for the white text labels and
pointers to various parts.

Mike Knudsen

 [ Thanks, Mike.  I'll place the image at http://mmd.foxtail.com/Pictures/
 [ -- Robbie

 - - -

  MUSIC PLAYED, RECORDED BY ELECTRONIC PIANIST
  from Electronic Design magazine, July 19 1977, page 21

The first electronic player piano replaces the familiar piano rolls
with magnetic tape recorded with digital data.  The Pianocorder selects
the grouping and sequence in which the keys are played by decoding the
data, and also controls how hard solenoids are actuated to drive the
string hammers.  Standard Philips magnetic-tape cassettes can be used
both to play recorded songs and to record, for example, a student's
piano lesson, and play it back.

Developed by Superscope, Chatsworth, CA, the basic Pianocorder system
will come either as a kit to be installed on any upright or spinet
piano, or as a "Vorsetzer" unit that can be rolled up to a piano
keyboard.  Padded fingers extend from the latter unit to press the
keys.

To minimize drop-outs and ensure maximum data reliability in either
the playback or recording mode, the cassette runs at 3-3/4 in. per
second -- twice the normal speed -- and at bit rates greater than
4-kbits/s.

To make original studio recordings, an 8080 uP-controlled system
samples each key as it is depressed.  Separate transducers on each key
monitor key displacement, actuation speed and the pressure on each
struck key.  This parallel information is then digitized and
multiplexed into serial format.  In playback, a logic panel delivers
this information to five driver-decoder PC panels via a bus system.

The Pianocorder system records and monitors 32 levels of intensity with
which a key is hit, and decodes this information to drive the solenoids
with a variable pulse width at full voltage.  The wider the pulse the
louder the struck note sounds.

 [ Note this approach to recording expression! -- MJK ]

To record on the home system, the sound intensity can be monitored
by a microphone.  The sound level from the microphone is applied to an
arithmetic circuit that samples, at any instant, the sound volume, and
the number of keys depressed.  This sampling is converted, using an
algorithm, into various sounds that mimic those of the original piece.

Volume production of the Pianocorder is slated to begin next January.
The kit is expected to retail between $1250 and $1500, while the
Vorsetzer unit is expected to sell for $1500 to $2000.

With either the Pianocorder or Vorsetzer units, a prerecorded library
of 100 45-minute cassettes will be furnished, many of them containing
recordings of piano-roll classics from a 15,000-roll collection of
Joseph S. Tushinsky, Superscope's president.

-- end --