...This is an article describing how to add this tuning process to your violin plates.
...Before this can be done you must have properly graduated and tuned violin plates
...The basic concept is that when your plates are tuned all over to the desired 'goal' plate frequency, your final step is to locate the overtone lines for the base tone plus 25%, base tone plus 50%, base tone plus 75% and base tone plus 100%.
... These lines are then left alone and the five areas thus described are scraped so that the overtone is the same all over that overtone area. When complete your plate will have approximately equal areas representing the musical parts of a perfect chord (tonic,major third,perfect fifth, minor 7th, and tonic again an octave higher).
...Keith Hill describes this adjustment to be the most important for defining tone to the completed instrument.
... Before you can apply this procedure, you need to get the tap tone even all over the plate first {which is different than plate overtones}.
[...I can testify that this procedure can be applied to violin bows as well, with wonderful results to the playing features of the bow. (bows have a similar overtone progression to that of a violin plate).
...More on this topic later...David Langsather 5/24/2007.]
...The following photos shows the overtone patterns that author Vigdorchik describes in his book on violin making. (Our Goal frequencies, however, are 322HZ for top and 353.5HZ for back plate). Notice that the two opposite corners have overtones an octave apart.
...You may furthur notice that the overtone series goes up from one corner of the lower bout to the opposite corner of the upper bout. If you tap along the center of the tone strips and the tone does not go up evenly, then it means that the plate overall tap tone is not yet even all over. Stop now and correct it so that it is even all over and at the correct plate frequency.
...in order to use Keith Hills' area tuning principle, we first determine where the overtone frequencies for plate tonic frequency, plus 25,50, 75, and 100% lie. Draw these lines on the inside of the plates for guide lines to help us apply the area tuning principle, as illustrated below:
double Tonic
Tonic +75%
Tonic +50%
Tonic + 25%
...Set of five maple tone blocks for back plate showing frequencies and where to top when looking to compare overtones.
Set of five top plate tone blocks with frequencies.
Close up of frequencies for back plate.
...The end of one low toned pencil taps the end of the reference tone block and the other pencil taps the plate immediately afterwards so our ear can compare the tap tones. Please note that you must select two tapping tools that are IDENTICAL in their own tap tone so that their differences do not throw off our hearing. All wood items have widely varing tap tones, even from the same batch of pencils.
...As a note of interest, as not everyone who reads this will have access to the equipment necessary to make and calibrate reference tone blocks; there is a way to do this by ear once the plate tone is even all over (not overtones however):
...Using your two perfectly matching tapping pencils; Use one to continually tap the tonic area of the lower bout and with the other, slowly move up the plate listening to the overtone generated.
...Initially, the overtone will increase, then level out and become somewhat indistinct. Next it will begin to go flat (like a string slightly low in tone) and then suddenly the tap tone will rise going through a perfect harmony note and slightly above that to go sharp in sound. Now tap back toward bottom of plate and exacltly identify the point of perfect harmony. Mark this exact point with a pencil line. This first point should be approximately on the tonic + 25% line shown in the photo above.
...Now repeat this process up the length of the plate tapping the tonic area with one pencil as reference. Once all four overtone lines are discovered and marked, then using each harmonic point as the new reference for tapping, move the line out to both sides of the plate beginning with the marked spot until the lines appear as in the plate photos above. Then tune the overtones as described above.
...I believe that with this information as a guide, you will have a fighting chance to to do an accurate job.
...As of this date (5/2007) I have not re-done one of my violins with this finishing method yet but I have done a violin bow which is done similarly as above and both my violin insturctor and I agree that it made a huge diffence in sound quality; so I have some expectation of possible positive success with the plate tuning (after maker Keith Hills useful information).
Note: tonic is at frog end and tip of bow repeats the tonic, with overtones an octave higher. Tape marks show overtone series of +25,50,75% which naturally occur when the bow is first tuned to produce even tones from end to end (ignore the overtone series).