Responding to Scotty Greene at DeBence Museum, regarding restoring
a Cremona G [140419 MMDigest].  I recently restored a Cremona "A"
roll piano, and may be able to help on restoring your G.  But I do
not have direct knowledge of a G, so these are educated guesses:

The "modulant" control you mention is the "soft" control on my "A"
piano, with positions for off, automatic, and on.  A valve block on
the inside provides the control.

The knob labeled "muffler"  on the left end of the case with the
eccentric on the inside, is, on my piano, for the felt rail.  I don't
see the felt muffler rail in your pictures.  I restored my felt rail
but decided not to install it.  The eccentric manually lifts the rail,
which is screwed to the inside of the case on both ends.

Your pictures didn't show any of the five other "instruments" that
the G roll piano should have.  Things like drums, xylophone, triangle,
tympani, pipes, etc.  I don't know which ones would be installed in
the bottom, and which ones would be installed in the top section of
the piano.  I'm guessing the unused tubing and valves are for those
instruments.  Perhaps sometime in the past those instruments were
removed and the tubing pinched off?  Other items controlled by the
stack valving are play, soft pedal, loud pedal, rewind, the mandolin
rail, and coin trip (on my piano).

A rather detailed dissertation of the restoration of my Cremona A roll
piano is in the Sept./Oct. 2011 issue of the AMICA Bulletin.

Contact me off list is I can be of any further assistance.

Ray Fairfield