I believe that for piano motors the usual power voltage was 90 to
100 volts.  This true in my parents' household, from 1939 to 1945.

Gradually the nation raised the standard to 105, then 112, then the
present 120 volts.  So the motor that expected 90 volts, now running
at 120 volts, has about 1.77 times the heat.  No wonder they fail.

My fix has been to use a transformer to lower the voltage applied
back to normal.  The step-down transformer can vary in cost from
a buck up to over 100 dollars depending upon the electrical knowledge
of the owner.

Will Herzog