I have a 1972 Baldwin spinet piano with a bright tone and excellent
sound and workmanship for an instrument of its class.  Living in
a small house it was rather loud, so to eliminate this problem I
installed a "practice rail."

Basically, one takes some sort of rail long enough to fit across the
strings of the piano, attach felt to it, and situate it so that the
felt sits across the strings where the hammers strike them.  This will
soften the sound, and should make most player pianos more suitable for
an apartment.

My piano tuner has a joke that they are called "lease savers" as they
are installed to quiet a piano's sound to avoid irritating the other
tenants and to halt complaints.

Clinton Gray
Hereford, Arizona