Tuning Barbells (A Weighty Subject!)
By Robbie Rhodes
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
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(Message sent Thu 16 Nov 1995, 02:45:38 GMT, from time zone GMT-0800.) |
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