There are three electrically powered things one can add to a player
piano: a roll drive motor, a set of e-valves and in the case of a
foot-pumped instrument, an electric vacuum pump.  My Ampico has had
a set of e-valves since 1978, and I have benefited from this by
having a much larger roll library that I would otherwise have had.

The instrument can play rolls, but the reality is that the e-valves
improve the performance by eliminating problems associated with the
primary valves.  So I only play rolls when demonstrating, otherwise
I listen to a playlist of my favourite Ampico e-rolls.

My Weber Pedal Electric Duo-Art (PEDA) is fast becoming a totally
electrified instrument.  Its original Motora pump has been replaced
with an Aeolian 'tugboat' pump, but why the pump in the first place?
To play Duo-Art rolls, and also Themodist rolls, which both require
the electric pump to be running.  I can also use the pump to assist
pedalling a player roll, although I usually don't.  So having an
electric pump in a pedal player was established many years ago, and
I have no problem with the idea.

I agree with Steve Marx that if a player is properly restored, it will
pump very easily, and therefore should not need the addition of an
electric pump.  But many instruments are not properly restored or are
becoming tired, and an easy way around the problem is to power it from
a vacuum cleaner.  Many instruments have this addition, often too
because the owner has dicky legs and is unable to pump loudly or for
long enough.

Then there are those who like to just listen to the music rather than
be a participant, such as Geoff Ward.  To me, making a player piano
more versatile is a great thing to do, as it ensures it will be used
more often, so adding an electric pump to a player has my full
approval.  One such installation uses a light dimmer to control the
vacuum cleaner, giving a degree of control and therefore expression.

The roll drive motor in my PEDA is now electric, as it was a simpler
solution than trying to adjust the motor governor to prevent the
motor slowing during pedalling a soft passage.  Most player roll motors
tend to vary in speed like this, where an electric motor drive does
not.  Of course, if properly adjusted and restored, this is usually
not a problem, but an electric roll drive has other advantages, such 
as no longer being powered by the foot pump.

When I finally get around to fitting a set of Bob Hunt's e-valves
to the PEDA, I will have perhaps the most versatile player of all.
I will be able to pump e-rolls or normal rolls, and play Duo-Art
e-rolls or rolls.  I can chose to pedal or have the electric pump.
With a bit of additional electrics, I will also be able to pedal _any_
MIDI file, such as recordings made on a Disklavier.  It simply requires
converting the pedal data into note data.

Not everyone will agree with me, in that originality is preferred.
But part of the joy of mechanical musical instruments is using them
to the full, and any mods I make are always reversible.  The result
is increased versatility, piano rolls are not destroyed and enjoyment
of the instruments is enhanced.

Peter Phillips
Sydney
http://www.petersmidi.com/