To eliminate moths, the piano should be disassembled and vacuumed
and brushed off thoroughly.  That is, all the action parts should
be cleaned, plus the keys and underneath the keys.  A moth-killing
spray is then applied to the felt parts.  This spray used to be
carbon tetrachloride but now is a less noxious compound.  Most good
hardware stores sell it.  You can then try carbon dioxide (CO2) in
the form of "dry ice".

Remove the lid, key cover and bottom cloth and seal the piano in
plastic.  You can get large bags used by furniture movers, or use
a plastic drop cloth sealed with packing tape.  Place dry ice (about
five pounds) in a couple of cloth sacks (pillowcases or bed sheets)
and wait a few days.  The carbon dioxide can kill the moths without
danger to you (as long as you stay out of the bag!).  Be sure the gas
can enter the interior of the piano.  You can repeat this more than
once.

Another option is to fumigate the piano, but this requires moving it
to the shop for treatment.  Export/import craters can tell you where
you can find such a service.

Philip Jamison
Pennsylvania