Oh, the difference that a half-turned screw can make!  This is just
an update on my Ampico A squeak.  Special thanks to John Grant for
his help.  I tightened the deck-to-deck bars slightly.  I also found
that the bottom deck stiffener wires were mostly stripped in place but
the wood screws stripped.  I fixed the stripped holes and re-installed
the wires.

Ta-da!  No more squeak.  I put the humidifier in the room for a week
just in case.  Thanks everyone for your help.

Adam Aceto
Burbank, California

P.S.: In John Grants' post he said "thin deck-to-deck support wires ...
about 1-1/2" long and 1/8" diameter, with looped "eyes" at each end
to receive the screws".  Actually, what he described here, at least
on my piano, were the deck stiffener wires.  And what he described as
horizontal "stiffener" bars of steel with rounded ends, about 3/16"
thick, 3/4 was actually the deck-to-deck supports.