Musical Box Tuning
By Chuck Walker
Responding to Jim Heyworth's questions re tuning disc box combs:
Disc box combs are not inherently "Sublime Harmony" as the two combs are structurally identical with respect to tooth shape and dimension. They may be, and I suspect frequently are, tuned slightly different from each other resulting in a slow beat on the order of 1 or 2 Hz. We have a 17- inch Stella that shows marked beats of this order and it sounds beautiful. Whether the combs were tuned this way deliberately or just done quickly without a lot of testing is open to debate but the end result is pleasing anyway.
They should probably not be tuned equal temperament. The combs may approximate a mean or just temperament. Since musical boxes play in only one key or its relative minor, the tones can be optimized for the best harmonic presentation.
A few (very) samples of some disc box combs here show stretching on the order of 10 to 20 cents per octave. It is difficult to really quantify this sort of thing as musical boxes sometimes show little stretching in the mid range octaves but the lower octaves will be stretched more to the bass and the upper octaves will be stretched more to the treble. I have measured some early key wind boxes that showed stretching on the order of 25 cents per octave across the comb. It seems insane but the boxes all sounded just fine and quite brilliant in tonal quality. If the box sounds good I would leave it alone. And thereby hangs a story.
Some time back I worked on re-tuning a key wind comb that had been sanded on the surface to improve its looks I suppose. The result as you can imagine was an acoustic and musical horror. Oddly enough, with the exception of some really wildly off pitch teeth, the main effect was to raise the treble end such that the stretching (I use the term loosely) was on the order of 40 cents per octave. This made the notes at the top roughly two and a half steps higher than the bass end. They were even too high for my old Conn Strobe tuner to register.
It sounded terrible ... except that after working on other problems and playing the box over and over for a couple of hours, the dang thing would begin to sound okay! But leave it alone for a day and my ear would return to "normal" and it sounded horrible again.
Message: our ears and psychological receptors to music can be trained to accept odd or unusual harmonic relationships as normal. I have thought about this a great deal and now limit work on really bad combs to short periods. It pays to be cautious. The end result of this comb was to reduce the overall stretch to about 20 to 25 cents per octave and of course correct any teeth that were obviously off pitch.
Jim, you are on the right track and have already transposed Graham Webb's data to your own situation. All combs may be a bit different from what is reported in the books. Good luck with the rest of it.
Chuck (current mossback of this group) Walker
cewalker@prodigy.com
Hopewell Junction, NY |
(Message sent Tue 18 Feb 1997, 04:47:24 GMT, from time zone GMT-0500.) |
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