Howdy, Fritz Gellerman, and welcome aboard.  I share your interest in
xylophones and the "melodic percussion" instruments.

The "cut up" on the back side of bar resonators serves these purposes:

1. To tune the fundamental (by grinding the pitch lower).

2. To help bring the most prominent overtone into reasonable tune;  if
the bar is coupled to a stopped resonator tube then the third and fifth
harmonics will be important.

3. Occasionally to force the nodes of the fundamental (and perhaps one
of the overtones) to a proscribed location, so that the mounting hole(s)
don't vibrate.

Many ('umpty-eleven) years ago ol' man Orville Cooper called me to his
workshop in Long Beach to help with a set of Deagan shaker chimes.  My
recollection is that Disneyland had purchased a second set for the
Main Street Quartet, and Cooper had contracted to fix 'em up.  "I carved
some new tubes and now we gotta tune them, Robbie."  And I gazed at the
craziest "instrument" I'd ever seen!

Some years later when I performed at Disneyland I got to see them in
action, and maybe you have,  too.  In mid-afternoon the Barbershop
Quartet would come around to Coke Corner, on Main Street, and I'd give
them a piano accompaniment for some songs.  Near the end of their routine
they would produce (from inside their voluminous jackets) the set of eight
chimes, each tuned differently, one for each hand.  Each chime rack
had three tubes hanging vertically, captive in a sort of cage, and when
the frame was shaken horizontally all three tubes would strike.  The
sound was exciting,  because the three tubes were tuned in octaves, and
loud, because each metal tube had a concealed built-in resonator!

Cooper had already rough-cut the replacement tubes, and one or two extra
for experimenting.  The bottom of the tube was plugged with a short slug
of steel (or was it lead?), but the top half had been sawn apart
vertically to split off a semi-circular piece.  I blew across the
stopped resonator (the bottom half) to get its pitch, which was pretty
close to the fundamental mechanical resonance of the structure.  Cooper
showed me the place in the musical scale where the new chime rack must be
tuned: "Ya gotta tune it to here."

So I experimented a bit and found where to grind in order to lower the
bar resonance, and also where to grind in order to raise the pitch of the
stopped resonator without affecting the mechanical resonance too much.
The last operation was to locate the mechanical node in the upper half
and punch a hole for the suspension thong.

The restored set of chimes looked good and sounded just fine, and I guess
Disneyland was happy with 'em.   Many years later a pipe organ fan told me
it was originally for installation in the "toy box" of big theater organs,
and that - to his knowledge - the chimes were never sold by Deagan as
hand chimes. I wonder if that's really true.

-- Robbie Rhodes