Hi Steve and MMD,  I have an English Duo-Art and the power switch is
beautifully made, but it would never pass today's safety regulations.
It is poorly insulated and the current running through it is quite high,
some motors taking up quite some amperes.

I didn't want to test if I would get a shock, but I'm sure I would
have sooner or later.  Instead, I've built a simple switch mechanism
on the back of the piano containing a solid state relay (SSR).  The
device switches up to 8 amperes and is powered by 5 to 24 VDC.  It's
relatively small and out of sight.

The 7.2 volts that powers the SSR comes from an old adapter and is
switched through the normal [Duo-Art] power switch, totally harmless.
It cost me 10 euros altogether as I had the adapter laying around.
If needed I can draw up a diagram.

Regards,
Niels Berkers
Arnhem, The Netherlands