Mike Kitner's article reminded me of an offbeat automatic shutoff
I built years ago.  The first player Chris and I rebuilt was an
1927 Baldwin Monarch, a nice piano with a commanding tone.  I added
a suction box to the player, and wanted to add an auto shutoff.
I tried many ways to do this, and many of my early designs did not
work!  <chuckle>

I installed a micro-switch on the double tracker pneumatic, in a manner
that it would stay "on" unless it was shifted to the extreme left.
I then installed a small adjustable counter-balanced spring that would
gently pull the double pneumatic off to the left when the pneumatic had
no suction and was at rest.  The spring was light enough so as not to
interfere with the tracker's normal operation.

The tracker was of the "floating triangle" type.  The tracker also
had suction in rewind.  I built a distribution block that reversed
the action of the tracker when the piano went into rewind.  I also
installed a larger gear in the upper roll chuck to slow down the rewind
speed to help preserve brittle old  rolls..

To start the piano, all you had to do is push a button long enough
to allow the suction motor to center the pneumatic, and turn on the
switch, or pump one of the pumping pedals.  The piano would play, then
rewind, and once the roll came off the take-up spool then the floating
triangle would dump ambient air into both sides of the pneumatic, and
the spring would gently pull the pneumatic off to the left, and turn
off the motor.

I sold the piano eight years ago, and the shut-off system still works
fine as of this writing.  Since then, I learned much simpler ways of
adding auto shut off, and probably will not do it again.

Later, I discovered that I had mistakenly covered the striking pneu-
matics and tracker on my first player with "Shultz pouch cloth"!
I worried that the thin cloth would wear out too quickly, but so far,
it shows no signs of wear.

To those of you who are prompted to send me a "you were a big dummy"
letter, I already know that.  I have been known to make mistakes.
I try to learn more, and go on about life.  If I am somehow seen in a
bad light about admitting this mistake on my first player, so be it.
But it does say something about the durability of that cloth though.

Cheers
Andy Taylor
Tempola Music Rolls