From my childhood I vaguely recall a couple of "B" movies.  One
involved a piano instruction system in which the salesman placed rings
on his fingers which were then drawn to the proper keys presumably
by magnets beneath the keyboard.  After the customer/victim left
the store, the salesman could be seen rewinding the roll on what
was probably a Duo-Art grand piano.

The other movie featured Phyllis Diller in the course of acquiring
a "Duckworth" player piano.  Essentially that's all I remember.
Can anyone supply additional information?

Jeffrey R. Wood