Sodium bicarbonate, liberally sprinkled over all surfaces and left
lying inside the piano in shallow trays, will often work wonders.  Also
wipe over surfaces with a strong solution.

Sodium bicarbonate also works for many other smells and on virtually
any surface including upholstery.

No need to buy the expensive culinary grade product.  Hardware stores
and some supermarkets usually sell a commercial grade in pound (kilo?)
containers under such names as "Odour-gone".  Look at the small print
to check the contents -- you do _not_ want any perfumes or other
additives.

By the way, I like the ozone method mentioned by Doug Rhodes.  I have
never come across this before.  If your piano has an electric pump you
can try this method for yourself.  Adjust the brushes on the motor to
maximise arcing (sparks generate ozone) and increase the supply voltage
with a transformer to make the sparks bigger still.  Leave it running
unattended for a few days.  Fit an oversize fuse and do *not* use a
ground fault interruptor.  And make sure your fire insurance is up to
date <GG>.

The author disclaims any liability for any of the advice regarding
ozone.

Jeffrey Borinsky