Often the lights are available to be on only during the playing _or_
all the time, at the operator's choice.  Some had small lights on all
the time and larger ones came on at the drop of the coin.

What you can do is wire a system to wire all the lights in series
during off time and a switch to put them in parallel when the piano is
playing.  This will give you a drastically lower light level (cooler)
until they go to full brightness during playing.  Some 'twenties houses
did this in ballrooms for dimming lights at several levels before there
were light switch dimmers as we have today.

D.L. Bullock
www.dougbullock.ws