I, too, had a situation where the tuning and cracked plate came close
together.  A 1927 Lester piano was tuned in the evening.  It sounded
great and there were no problems while tuning.  The next evening I put
on a roll to find that something was drastically wrong.  I opened the
lid and discovered the plate had cracked.  My wife said she heard a
loud bang during the morning but assumed it was noise from outside.

I understand that a plate can't crack from tuning, but what a
coincidence that the piano was tuned and a few hours later the plate
cracked.

Tony Liene

 [ Diane DeTar had the same experience with a Lester piano.  She
 [ found that the plate was already cracked before the tuning, and
 [ the slight increase in tension after tuning was the "straw that
 [ broke the camel's back!"  -- Robbie