This is an interesting concept.  As you say, there is no theoretical
reason why a solenoid couldn't duplicate human performance.  I think
I'd drive the solenoid with a synthesized waveform, made by turning
its driver on and off at a high rate and varying the width of the on
time.  Since the mass of the armature cannot respond to these fast
pulses, it has the effect of giving infinitely variable force curves.
In this way, very high efficiency can be attained since there is almost
no power lost to heat in varying the current to the solenoid as would
occur with an analog driver.

I've daydreamed of letting a computer analyze a sound recording,
then breaking the notes down and playing them.  If the same computer
was equipped with a microphone input, it could be self-calibrating,
constantly modifying the output to more nearly duplicate the recording,
thus compensating for differences in pianos and rooms.  This would
solve the problem of no roll library -- feed it an audio CD of Van
Cliburn!  And writing routines to emulate various pneumatic reproducers
should be straightforward, then you'd inherit the existing roll
repertoire.

The problem, of course, is that there is not enough market for such
a device to justify the terrific amount of software development that
would be required.  The hardware technology is already readily
available and wouldn't be terribly hard to implement.

I'm very new to this hobby and have been voraciously reading
everything I can put my hands on.  I just bought a 1930 Chickering
with the Ampico B that I haven't even received yet and am looking
forward to restoring it.

Can anyone tell me what the latest news is on the Power Roll?
I have read what I could find with great interest and think I'd like
to have one.

Travis Martin