Hi gang,  Well, the Mills Piano uses solenoids and seems to give good
results, however these are relatively high-impedance devices that operate
with approximately 110 to 125 v.d.c.  As a result they perform faster
than if they were low impedance devices operating on 10-15 volts as most
pipe organ magnets and Wicks Direct electric magnets do.

This is something that Mills and others worked out very early and so
incorporated it into their Violanos and Pianos.  Some people think it was
merely because 110 v.d.c. was more commonly available and that may have
been a factor but it is also true that since about 1890 reliable rotary
convertors were available for organ use that could have easily been used
by Mills had they so desired.

We don't ordinarily think of electricity as having mass but it can behave
that way in some applications.  The current flow is the equivalent of
mass while the voltage is the amount of potential, or electrical
pressure, that moves the current through the circuit.  Thus with higher
voltage and lower current, i.e., higher impedance, you will get a closer
to instantaneous response.  This is especially noticeable when there is
mass that has to be moved, such as the armature of a solenoid.

Hal Davis