With regard to Eli Shahar's March 26 posting, I would like to point out
that the tiny pneumatics mounted on each spring pneumatic each need to
be teed into the line that supplies suction to the sustaining pedal
pneumatic.  Thus whenever the sustaining pedal is activated, these
pneumatics tend to counteract the force applied by their associated
spring pneumatics.

The objective of pedal compensation is to achieve better pianissimo
playing.  Further information on this topic can be found in an article
I wrote for the April, 1982 issue of the AMICA bulletin.  Included are
excerpts from original written material prepared for by E. S. Werolin,
who headed the Ampico service department in the 1920s.  

The article can also be found in Volume V of the AMICA technicalities.
AMICA members can access these materials in the "members only" area of
the AMICA web site at http://www.amica.org/ 

Dave Saul