Hi Dean,  Yup, I learned all about living in a region with 12% relative
humidity.  When I moved my upright Marshall & Wendell to the desert it
played for a while and then I never even heard a dying gasp.

The main problem with my Ampico piano was the two large screws
that clamp the stack together.  When I got into the ailing machine
I found I could tighten the nuts holding the stack almost a full turn.
Tightening these brought the player back to almost useable, but the
expression units are made of soft wood, and there are a number of
small channels and a valve that needed rebuilding.  I don't know if
the rubberized cloth was affected by the dry air.

My Weber Duo-Art piano didn't suffer from the climate change very
much.  I did need to change the spring tensions.  Duo-Art used much
harder wood, probably maple.  Maybe that accounts for the difference
in the pianos.

You may find that screws throughout the action need tightening.
No doubt the valves will change dimensions, but I did not need to
alter the valve clearances.  They are made of soft wood, but are
usually coated with heavy shellac.  Whether the valve body shrinks
or expands, I don't know.

Bill Chapman
La Quinta, California