Several folks have talked about converting piano rolls to MIDI which
seems to me to be a tough job compared to the following:

Player pianos operate by physically depressing the piano keys.  This
takes considerable force.

That same force could be used to depress the keys of an electronic
synthesizer which takes very little force.

So, let the piano keys drive the synth keys and you get not only the
the piano sounds but also any of 120 voices of the synth, including
splits and layers.

Any number of simple mechanical linkages between keys are conceivable.

Put on the thinking caps.

Dwin R. Craig
Frederick MD