Craig, you seem to get to restore at least one of everything!

I agree that preserving original power wiring must take second fiddle to
safety, and will check out the BX armored cable wiring in my Duo-Art
grand.  I don't think 3-wire ground power cord is needed for a mostly
wooden instrument on a wooden floor, but fused plugs seem like a good
idea.  Fused plugs used to show up on amateur radio transmitters in the
1950s, but I haven't seen one lately.  BTW, there was a huge orchestrion
(one of Welte's largest models?) in England that burned itself up from a
wiring short.

As a collector/restorer of antique home and "ham" radios, let me offer
our usual solution -- use one of those multi-outlet power strips with its
own switch and circuit breaker built in.  Just switch it off when not
playing any instruments.

Even neater, plug your instrument into an outlet that's controlled by a
wall switch, as intended for a lamp.  Keep a lamp plugged into the same
outlet to remind you when the power is on.

If you work on instruments on a concrete slab floor, by all means use a
GFI receptacle to protect yourself, not the machine.

About Craig's DC control issues:  First, the most effective arc
suppressor on any inductive load (relay coil, solenoid, magnet) is a
diode connected across it.  It should be wired backwards to the applied
voltage so no current will flow from that -- but when the circuit is
opened, the coil's desire to keep current flowing will reverse the
voltage and the current will flow through the diode, instead of building up
a high voltage that causes sparks.

You can get little 400 PIV (peak inverse volts) solid-state diodes at
Radio Shack for 2 for a dollar, more or less.

The catch is that since the diode slows down the decay of the coil's
current, and hence its magnetic field, the magnet doesn't let go quite as
fast as without the diode.  This could mar the musical performance of a
Violano or other instrument, much like clogged bleeds causing slow
repetition in a piano.

But you can adjust the trade-off by putting a resistor in series with the
diode.  The larger the resistor, the quicker the release but the more
arcing.  Experiment to suit your needs.  Diodes of course are for use
only on DC, not AC, coils.

About solid-state relays:  I've seen them successfully switching 115 VAC
without problems.  However, I think certain types will not work on DC --
they'll turn on but not off!  These depend on the zero-current intervals
that occur 120 times per second to turn off their semiconductor switches
(100 times/sec in Europe).  "Pulsating DC", which you get from a
full-wave rectifier running off your AC power, will have these
zero-crossings and turn off OK, but "pure" steady DC from a motor
converter may not.

Finally, there are high-voltage transistors that can switch 120 volts DC
directly.  These could be drawn from the Violano's brushes with very
little current, no noise and no delay (unlike relays).  Just don't even
think of using them without diodes across the driven coils, or the
transistors will "punch through" and short out the first try.

Mike Knudsen