[ In the 110208 MMD Robbie Rhodes appended to Stephen's posting on this
[ subject: "Dave Bowers, in the book "Put Another Nickel In," says that
[ a few Wurlitzer LX instruments were fitted with a xylophone as well
[ as the 14-note bells, and the APP rolls had multiplexed controls for
[ both the bells and xylophone.  What notes does the xylophone play?
[ Where are these instruments today?"

The one xylophone-and-bell instrument known to exist is in the San
Sylmar collection of J.B. Nethercutt, otherwise a standard LX.  In
addition to the standard APP 14-note bell unit, it plays a very small
scale reiterating xylophone, probably a unit left over from the
xylophones used in the earlier Bijou Orchestras.  It is operated by the
simultaneous on/off controls of the pipes, which I believe are holes 72
and 73.  The bells "on" was controlled by the simultaneous punching of
both on/off  notes for sustaining pedal.  The "off" that was used by
the bells is shared by the xylophone: system holes 2 and 3
simultaneously opened and individually controlled soft pedal and
mandolin on/off.  These multiplexing mechanisms are very delicate and
may require the addition of pneumatic restrictors, increased valve
travel, and sometimes pouch-assist springs; even then they may be
unreliable, depending upon vacuum levels in the piano.

At least two different methods were used: the more common multiplexing
system using the pneumatic slider blocks, and the five-pouch block, (no
slider block is found in the IX-B and I-B).  When the bells' double
notes turn the unit on, a wonderful solo-like section is heard, using
specially arranged alternating thirds and sixths, imitating a skilled
human bell player.  The xylophone passage seems to play the same
arrangement as the pipes and piano notes.  Not every selection on the
post-1921 rolls uses the bells, and fewer still the xylophone.

Stephen K. Goodman
Tarpey Village (Fresno/Clovis) Calif.
http://www.mechanicalmusicrestoration.com