Granted, I have never added a xylophone to a foot-pumper player.
I have only restored a few foot-pumper type player pianos.  The
masters at cramming extra instruments into tight spaces has to be the
Nelson-Wiggin company.

A folded xylophone design would be one of my choices.  One might
consider the xylophone that lays flat in the top of piano above the
spool box, another Nelson-Wiggin design that was used in the Casino X
model.  Someone might consider adding an attractive cabinet to the top
of the piano or side chest.

I would consider turning it on or off with a button in the keyslip by
the tempo control.  I might even consider adding a snare drum and other
percussion effects also controlled by a button in the keyslip to add
more pleasure for the aspiring musician playing the player piano.  Gee,
before you know it you could have a nice homemade photoplayer at your
fingertips.

There were several photoplayers that played 88 note home-style player
piano rolls.  Think of the fun.  I am so excited about this idea I may
go out and start building one tonight. ... Well, not tonight, as I have
to finish a couple of Seeburgs first and then there is that Wurlitzer
in the corner staring at me...

Don Teach
Shreveport, Louisiana