For the past winter, and for the first time, I experimented by keeping
my Ampico under a tent of plastic sheeting, keeping the lower household
humidity away from it.  Under the tent, I kept four flat pans of water
that I kept filled.  In addition, I kept an accurate hygrometer under
this tent, closely duplicating the percentage of humidity of summer
(35% to 40% relative humidity).

I checked it every day to be certain the percentage of humidity
remained within this range.  The piano has not been tuned in one year.
Today, I checked the tuning and was very pleased to find the piano did
not require much tuning at all, other than a few unisons that were
slightly out.

Some ask why I cannot raise the humidity inside the house in winter,
and not have an unsightly tent over the piano.  The answer is old
houses cannot take an increase in the inside humidity in winter without
some consequences, be it condensing in the house insulation, attic,
walls or windows in rooms that are cooler than the remainder of the
house.  I suspect this is true of modern houses, too.

In past winters, I kept containers of water in and behind the piano,
and in summer gentle heating rods inside and behind the piano but
I found they are not enough.  Each year required major changes and
several tunings both winter and summer to get the tuning stabilized.

I find the tent method to out-perform the sophisticated commercial
units.  In summer the humidity can reach close to 90% so I use a
dehumidifier that can easily dehumidify the entire room and keep it
close to 35% to 40%.

Bruce Clark