As Stephen Goodman wrote, Wurlitzer didn't begin adding optional bells
to their pianos until the early 20's.  By then, the 75-hole APP roll
was well established, without room for activating a separate bell
register.  What to do?  Wurlitzer cleverly created a multiplex
arrangement using a combination of the sustaining pedal on/off
registers to activate the bells.  The pedal register still worked
normally, as the parallel perforations were slightly longer for the
pedal "off" register, thereby activating the bells but having
no affect on the pedal.  To cancel the bells, Wurlitzer used a similar
arrangement by multiplexing the hammer rail/mandolin on/mandolin off
registers.  Bells were usually a 14- or 16-note set in the upper
treble, sharing piano notes.  When the bell register was activated,
Wurlitzer normally used a tremolo or marimba effect in these notes,
which sounded a little like a second melody, similar to a Clark
xylophone-enhanced A or 4X roll.

From the early 20's on, Wurlitzer APP rolls used a combination of QRS
masters and original Wurlitzer arrangements.  They would appear
randomly, with some 5- or 10-tune rolls being , or mostly, one or the
other, and many rolls being a mixture of the two.  The Wurlitzer-
arranged APP tunes always sounded very different from the QRS versions,
and seemed to be arranged by the same person(s) as their 165 band organ
arrangements, because they often sounded similar.   I much preferred
the Wurlitzer arrangements.  Bell registers were almost never inserted
in the QRS-master versions, which were identical, but shortened,
versions of the QRS 88-note roll.  Many Wurlitzer versions had the bell
registers, which usually played one or two verses or choruses on each
tune.

In the mid 20's, Wurlitzer added optional 14- or 16-bar xylophones to
some style L or LX pianos.  Some also had bells, but it would not do to
use the same register for both.  What to do for a separate xylophone
register?  Again, Wurlitzer cleverly multiplexed a combination of the
two pipe registers to activate the xylophones, thereby enabling a
separate register not part of the original APP scale.  The xylophone
register was cancelled by the same multiplexed cancel register as the
bells.  The effect was to activate bells or xylophones in any
combination.  Unlike the bell register with the treble tremolo effect,
(and even though the xylophones shared the same piano notes as the
bells) the xylophone register would usually activate toward the end of
a chorus with the percussion and the louder violin pipe register.
Xylophone registers appeared from about the mid 20's in very few
Wurlitzer APP rolls.  It seems that the number of pianos that Wurlitzer
produced with xylophones was quite small compared to those with bells.

By the 30's, Wurlitzer was still using a combination of QRS masters and
their own APP arrangements, but the use and style of bell and xylophone
registers had changed, probably as Wurlitzer's arrangers had evolved.
From the late 30's on through the Ralph Tussing TRT era, APP rolls
seemed to activate the bell register much more frequently in most
tunes, but the xylophone register was rarely heard.

There is no way to tell by looking at a 20's or 30's APP roll whether
the tunes are QRS or Wurlitzer arrangements, and whether there are bell
and/or xylophone registers in the tunes.  One must play the roll to
see.  Since my two Wurlitzer APP pianos have bells and bells-and-
xylophone, I'm careful to catalog my rolls to show the mix of QRS and
Wurlitzer arrangements, and also whether they contain bell and
xylophone registers.

Glenn Thomas
Princeton, NJ
www.nickelodeonhouse.net