There have been questions regarding the use of iterating vs. non-iterating
Xylophones and Glockenspiels.  Those instruments that have original
equipment iterating Xylophones were designed to use rolls that could also
be used to play another set of pipes thus the difference between that and
the "4-X" rolls that were cut specifically for use on machines with a
non-iterating instrument.  The iterations are actually cut into the roll.
It is for this reason that 'single stroke' or 'non-iterating' Xylophones
and Glockenspiels don't play properly when used on instruments with "A"
rolls or with "G" rolls.

The reverse also obtains when a "4-X" roll is used on a machine designed
for "G" rolls.  You can always remember, on the "4-X" roll the first
additional instrument is usually the single stroke Xylophone while on the
"G" roll the first additional instrument is the first pipe set, usually the
Flutes, if there are two sets.  I have played "4-X rolls on the Seeburg in
place of the "G" rolls just for the interest of it.  Later, I played the
corresponding "G" roll and there is a noticeable difference.  I have also
played "G" rolls on my Nelson-Wiggen "4-X" machine and can notice the
obvious shortcomings that way, too.

My suggestion is merely this, play your "G" and "4-X" rolls on whatever
you desire but allow for the differences when you judge the sounds coming
out of the instrument.  Of course, if you have a Xylophone on an "A" roll
player it should be of the iterating type.  I don't know of any "A" rolls
that were ever made for a single stroke Xylophone.

Musically yours,

Hal Davis