To all:  Just grounding the motor of a grand piano isn't the whole
thing.  I just checked the drawer switch of my Marshal and Wendell
Ampico and found that the motor on/off wire is contained in a small
metal J-box.  This little box has a toggle switch that turns the motor
on or off.  The toggle switch is activated by a brass (conducting)
lever that trips the toggle switch.  This is also a potential shock
hazard if not properly grounded.

Of more concern are the old PPCo breeze box controls in a round tin box
that was mounted under the keyboard of a piano.  The wiring, now almost
30 years old, is old zip cord that is getting brittle and falling
apart. The least someone should do when encountering these things is to
check them carefully and replace the original with a 3-wire cord with
the ground wire connected to metal on the round box under the keyboard.

Electrical standards were established because somebody got hurt or
electrocuted at some time or another.  They may be an overkill in some
folks mind, but it is best to err on the side of safety.  There really
is a reason that the green third wire should be connected!  (It isn't
that hard to do.)

For those who insist on authentic old wiring, then make sure that the
piano is plugged into a properly installed and functioning GFCI outlet;
they cost less than 10 bucks.  This is today's common sense.

Been bit a few times, isn't dead yet...

Larry Emmons