Hi Brian -- Although the problem in that player may be due to a
maladjusted governor, it sounds like the wind motor accelerator may be
leaking past its valve, causing the wind motor to have a mind of its
own.

This valve is usually controlled by the play-rewind lever.  It is
supposed to completely close when playing.  To test this, gently push
back the lever toward rewind without causing the piano to go into
rewind or engaging the stack cutoff.  If the wind motor speeds up at
all, that valve is out of adjustment.  If adjustment does not have any
effect, you might have to take it apart.  Check it for positive
seating, make sure there is no cracks anywhere, and make sure the
spring that pushes down on the valve isn't broken or weak.  Hope this
helps.

Best Regards

Andy Taylor
Tempola Music Rolls
http://home.swbell.net/tempola/index.htm