About thirty-five years ago I built up an accordion-piano that played
using Mills Violano Virtuoso rolls.  There was no difficulty making the
accordion express very much the same as a violin would have.

I simply used the suction to operate the accordion against spring
tension and controlled the suction with an "accordion" pneumatic in
a manner similar to the expression control from a Duo-Art reproducer.
There were, of course, only five levels of expression, i.e., Very Soft,
Soft, Normal, Loud, and Very Loud.  It was necessary to make a
five-level unit instead of four-level as in the real Duo-Art, and not
necessarily in the same 2:1 ratio of the Duo-Art controller from step
to step.

The 44 notes of the piano section of the Violano roll were coupled an
octave at both ends so that it played a total of 68 notes on the piano.
The expression for the piano was the same as used in the Violano
Virtuoso, although it was entirely suction operated rather than
electro-magnetically operated.

All who heard it thought it sounded great.  It went to a restaurant in
western New York State and I heard about twenty years later that it had
been destroyed in a fire, but for some years it performed flawlessly.
At least, that's what I was told.

Hal Davis