If I remember my high school physics right, when a gas is compressed,
its temperature rises.  As it decompresses, it cools.  Isn't that what
happens in a player piano?  Isn't a controlled partial vacuum the
method of why a player works?

It seems to me that as you pedal your player, you are actually cooling
the air running through it, as well as getting the enjoyment of the
music.  If all the owners of all the players out there used their
pianos more, maybe we would need air conditioners less, thus saving
on electricity bills.  I believe that when player pianos were in their
fullest popularity, there were many fewer air conditioners than there
are now.  Perhaps, because of players, they weren't needed.

Jeff Davis, in algae-green Seattle

 [ Trouble is, I heat up when I'm pumping the player, 'cause I'm
 [ supplying the energy for that pneumatic refrigeration system.
 [ The overall result is the room gets warmer.  ;-)  -- Robbie