I really appreciated all your suggestions for different methods to
reduce the sound from a player piano (and some of the funny comments)
but in the end I came up with a solution which no one had thought of.

As most of you piano aficionados already know, the lower and upper
expression pedals dampen the sound by moving the hammers closer to the
strings thereby reducing the acceleration of the hammers (someone did
mention this in a posting), and therefore reducing the sound generated
by the hammer striking the string.

So, if this is true, then moving the hammers closed to the strings
should reduce the sound even further.  I folded some cardboard and
wedged it between the bars holding the hammers and the fixed section
where the bars return to rest and this allowed approximately 1 inch
(25 mm) space between the hammers and the strings.

Eureka!  This reduced the sound by at least 50%, but had little effect
on the musicality.  Admittedly the expression controls are disabled,
but as the player is mainly used for sing-a-longs this is not important
and the pieces of cardboard can be easily removed if expression is
needed.

It should be possible to alter the throw of the expression levers so
that this same controlled effect can be achieved, however as this is
not my piano I didn't want to undertake any major modifications.

Needless to say the management of the retirement village are delighted
with the result and have invited me to move in when I am ready (which
will be in about a month, the way I am going)!

Best wishes to all,
Neil Stevenson (from Down Under)
Canberra, Australia