[Dixielandjazz] Irving Berlin's piano

[Edgerton, Paul A]

I read somewhere that Irving Berlin preferred playing on the black keys, but
that doesn't mean he could only play in one key. Could it be significant
that the black keys, by themselves, comprise a pentatonic scale?

The mechanism to shift the piano keyboard already exists on grand pianos:
the so-called "soft" pedal, which shifts the entire action to one side so
that the hammers strike only one or two of the strings in each unison. It
wouldn't be too difficult provide a pedal that shifts the action all the way
over to the next unison, thus transposing the keyboard by a half step.

Whatever Irving Berlin lacked in keyboard proficiency, he certainly made up
for it in melodic sense.

Paul Edgerton,
who wonders if that could be regarded as a prepared piano?