Hi All,  I would like to hear from anyone in the group who has
experience with operating a player piano (or other vacuum operated
mechanical musical instrument) at altitudes around 8500 feet.
Naturally, the concern/question is whether there will be any
performance problems as a result of the lower air pressure.

Mainly, I'm interested in practical experiences as opposed to theory.
However, since I was unable to find anything in the Archives about the
topic, it might be nice to add theoretical information to the database
as well.

What I was able to find out is that the atmospheric pressure at 8500
feet is about 11 pounds per square inch absolute (psia)* as opposed to
14.7 psia at sea level.  Theoretically, this means that the pressure
'pushing' on the surface of the bellows cloth and pouches is reduced.
And, since the air is thinner (or less dense), it would seem that it
would be easier to create vacuum.

However, my general feeling about the whole matter is that everything
is basically relative.  Therefore, the difference in overall performance
would be negligible.  Also, it seems that if an altitude of 8500 feet
was a problem for player pianos, my customers in places like Mexico City
(7240 feet) would not be buying music rolls.

* Ref.:  http://www.fluidedesign.com/solved_pumping_problems.htm#q42 

Musically,
John A Tuttle
Player-Care.com
Brick, New Jersey, USA

 [ 1 atmosphere = 14.7 pounds per square inch, which lifts a water
 [ column approximately 33 feet.  The typical player piano functions
 [ on a (differential) pressure of 1 foot water column or less.
 [ -- Robbie