Assuming the pins are tight, I have always tried to 'set' the pins and
deliver a reasonable 'blow' to the respective key.  Setting the pins is
to raise the string pitch slightly higher then ease the pin to the
correct pitch.  This takes the unwanted torsion from the pin shafting
which can be on the verge of moving if were to raise the pitch and not
ease back.  A run with the fingers likened to playing a harp can been
done across the strings to also 'settle' the strings 'friction' around
the pin block etc.

My knowledge on this was gained by Art Reblitz's book, "Piano Servicing,
Tuning & Rebuilding"; see pages 47 and 48.  I have always had success
with pianos staying in reasonable tune for longer than expected.

Spinet pianos should never have been invented, and whatever you do with
these "short stringed" instruments never works out to satisfaction.
We all know that the 9-foot concert grand piano is the easiest to tune.

Stephen Bentley - SB-"0" rolls.
Vancouver, British Columbia, Canada