Hi All,  Low humidity can certainly be a major problem, especially to
player pianos that haven't been "totally" restored.  One of the most
common problems I encounter while working on such units is general
looseness throughout the entire unit.  This situation is exacerbated by
forced-hot air heating systems that typically reduce the relative
humidity to less than 15%, and sometimes even as low as 8%.

I believe that the best time of the year to tighten aging player and
piano actions 'is' during the Winter.  And the only possible negative
I can think of would come as a result of 'over-tightening' the screws
(and/or nuts & bolts).  I've never experienced a stripped screw or a
cracked part that was the result of my tightening the unit during the
Winter.  (Then again, I'm not a big strong man with a guerrilla death
grip either.)

Typically, 12-15 inch-pounds (not foot-pounds) of torque is adequate
to tighten the majority of wood screws in a piano or player action.
The term I use to explain tightening to people is, 'snug it up firmly'.
Naturally, it helps to use the correct size screwdriver for the job at
hand.

In our home/shop, I find that individual room humidifiers work very
well, and they 'pump' about 2-3 gallons (per unit) of water into the
dry air everyday.  This raises the humidity to an acceptable 35%-45%,
which is much more healthy for all 'living things', including the
pianos, the furniture, etc., etc.

(By the way, these units are filled by hand, so there's no worry about
an automatic shut-off valve failing.  Years ago, I did have a system
that was hooked up to the heating system, and the auto shut-off valve
did fail.  It filled the basement with 2+" of water in less than 24
hours, causing thousands of dollars in damage to piano actions, spare
parts, etc.  Thank goodness for insurance!)

While in Boston late last year, I saw an interesting device that was
specifically designed to help maintain the humidity level in grand
pianos.  (It's so simple it definitely qualifies as a DIPUTS-type
product: DIPUTS: design ideas predicated upon technical simplicity!)

All it is is a plastic tube that's about 2" in diameter and about 3'
long with about 20-30 5"-6" slits about the width of a table saw blade.
The tube is stuffed with what looks like foam rubber.  To use it, you
simply put it in a bathtub or large sink and saturate it with water.
Then turn it upright and allow the excess to dip out.  Then you place
it inside the piano near the tuning pins.  (I can see people cringing).

I saw the unit in operation inside of a beautifully restored Steinway
Duo-Art, and the owner was delighted at how well it worked to help keep
his piano in tune.  As I recall, he said he had to 're-wet' the
'humidity stick' every week or so, depending on how dry the air was in
his home.  Unfortunately, I don't have the name of the company who made
to unit, or the name of the product, but it certainly isn't rocket
science.... just good old common sense.  Oh, I do know that it was
manufactured in Germany!

Musically,

John A. Tuttle