The jazz flutes in a dance organ should be tuned with the tremulant
switched off.  The pallet operated holes in the back of each pipe will
therefore be closed.

Jazz flutes are sometimes played with the tremulant off, according to
the arranger's wishes, so tuning any other way will make this rank out
of tune with the rest of the organ.  This may not be the case with all
organs as some may have just a single key to engage both the pipe rank
and the tremulant, but the organs with which I am familiar have separate
keys for each.  I admit that it is rare for the jazz flute to be played
without tremulant but it is done on occasions.

Sincerely from the centroid of Great Britain,
Nicholas Simons