John, In quoting me out of context, you failed to indicate that despite
its shortcomings, "I like my solenoid system".  With that said, let's
also observe that there's no vacuum pump noise in a solenoid system.

The biggest potential problem with pneumatic MIDI pianos is the
expression control.  Real performances do not lend themselves to the
left-half -- right-half stack pressure control design of the 20's.  A
consequence of this is that real performances, recorded in MIDI, are hard
to convert to the pneumatic coding method of Ampico, Duo-Art, or Welte.
I know.  I've tried on Mike Ames' MIDI-ized Ampico.

What's needed is either:  1) a pneumatic system which provides velocity
control for each note (using a new kind of valve design, possibly with
some kind of electronic feedback, or 2) a solenoid design which provides
velocity control for each note (using a new kind of driver design,
probably with some kind of electronic feedback.

Did you notice that both systems suffer from the same shortcoming?  The
truth is that both the Boesendorfer SE and the Yamaha Disklavier Mark II
have per-note velocity control.  Cost has been the limiting factor in
after-market electronic actuator designs.

Further note that self-calibration of ANY electronic system should
be possible by having a software calibration routine built-in which plays
each note and listens with a microphone or other feedback device.  The
Boesendorfer system has this.  I don't know about the Yamaha system,  but
its well within the technology.  (Clearly a "modern" electro-pneumatic
system could (and should) do this as well, to calibrate itself).

There are some wonderful things happening in the world of magnetic
materials (for disk actuators, motors for cars, etc.), the cost of power
electronics (for controlling such things), and a continuing decline in
the price and improvement in speed of micro-electronics.  I expect that
we'll see a continued improvement in electronic piano actuation systems.

I'm predicting that the dominant form will continue to be the direct
electro-magnetic actuator (perhaps not a solenoid but some kind of linear
motor).  Even if a velocity-per-key pneumatic system is developed, I
expect it will be a maintenance problem, but I'd be pleased if I was
wrong.  In the mean time, _MY_ piano is played with solenoids.

By the way, my 1984 electronic fuel injected Toyota Camry is still
running with its original fuel injection system.

Jody Kravitz