This is a very tricky subject.  I am a museum professional with
experience in most areas of conservation.  Relative humidity is very
important in the storing, display and the control of deterioration of
all historical objects.  The most important point is not to have huge
fluctuations in either temperature or humidity.  This means a constant
temperature and humidity level -- no peaks and troughs.

The recommended Relative Humidity for museum collections is 55% plus or
minus 5% in any 24 hour period.  The temperature should be around 20
degrees Celsius, again plus or minus 2 degrees in any 24 hour period.

Constancy is paramount.  Mechanical instruments are complex and are
made up of many materials.  If it is too damp we will have a rust or
corrosion problem; too dry and the wood will shrink, glue joints will
crack, and, for example, soundboards will split and actions in pianos
will become sloppy and unplayable.

I have experience with Dampp-Chasers and in the main _I do not
recommend them._  I have seen them put above the keys directly under
the wrest plank in a grand piano with the resulting affect of loose pins
and in some cases a split plank.  Some people put them under the piano
between the posts and close to the sound board.  The result is splits in
the sound board, loose bridges and ribs.  Others, again, put them inside
the piano, screwing them to the rim halfway down on the straight side in
a grand.  This is probably the best place _if_ the lid is kept closed.

In an upright, put in the lower section of the piano.  But *beware* :
if you dry out a player piano, well, you will be running the 4-minute
mile next time you try to pump it.  It will be leaking everywhere.

Again I say, constancy is the most important factor.  I have a great
worry about some of these historic instruments, such as large
fairground organs (band organs) being played on the rally field.
They are generally in a lorry or van, the sun is heating them up and
the air being pushed through the blower is being warmed.  This will
cause problems to the pipes, reeds, chests and, in fact, the whole
instrument.

I sometime wonder whether such enthusiasts care at all about the
preservation of such an instrument, but just the kudos of owning
something like that and the noise it makes.  These instruments are
no longer new but most at least 100 years old and the materials have
lost their suppleness.  Enough of me being controversial.

I should add that, apart from having formal museum training to
postgraduate standards, I also have qualifications in musical
instrument repair and construction.  So I am in an excellent state
to make such comments.

May I recommend the book, "The Museum Environment", I think it's by
Stolow.  It is a large book published in the UK by Routledge, and
covers all areas of care such as Temperature, Humidity and Light
levels.  I am always happy to give advice; just email me.

Jonathan Holmes (UK)