... For a top plate, I recomment that you tune the plate before you cut out the "ff" holes. cutting out the sound holes will not change the actual frequency but it will change the overtones; it is easier to tune the plates now. Notice the sound post pad which is left slightly thicker (to eventually match the back plate tone).
...Now suppose that just the outlined area is too high in tone compared to the rest of the plate which is at the frequency that we want it to be at.
...In this case, tap the too high area with your special tapping pencil and hear where it is the highest frequency. Beginning there, gently sand or scrape this area widening out as this area is lowered until the entire area matches the rest of the plate
...Now let us suppose that this area (outlined in blue) is too low in tone, but the rest of the top plate is at the frequency that we want:
...The solution will be in two steps. First the area in red will be lightly sanded and scraped until the blue area is raised to proper frequency.
...Now when the blue area is corrected, you will discover that the wood area between the two colors is now also raised in tone. Since it was previously at proper tone, now it will be too high (the area in green). and should be lowered to match the plate tone by carefully sanding and scraping (constantly checking with our tapping pencil... just a very quiet tap is what we need to hear).
...This is the procedure for moving the plate tones to where you want them. If you have a specific problem, please write to me and I will explain how to deal with it. The above examples, applied in various combinations should enable you to even out the plate tone to an high degree of accuracy.
...The one extra wide strip in the center is different in that the entire surface of this strip is adjusted to the same even tone (see green area above).
...Now the very interesting phenomenon is that if the plate is adjusted to be perfectly even in tone; A light tap (with our special tapping pencil) along this purple line and in the center of each of the penciled in strips (see red dots) will produce (at least to our ears) an octave progression of plate overtones by musical 1/2 tones (that is twelve steps in total) with the low tone in the indicated corner of the lower bout and the highest tone in the indicated corner of the upper bout.
... I believe that although the plate (or base tone) is even, because of the different overtones in differing areas of the violin plate ( due to the shape of the plate), our ears clearly hear this progression, whether on the inside of the plate or on the outside; and whether the plate is open or glued together with the rest of the violin body.
...Tapping the opposite corners should produce an apparent octave difference in tap tone.
...This information is useful because if the wood is perfectly uniform, and our graduating if perfect, then this Vigdorchik pattern is automatically produced.
...Now let us say that after we adjust the Vidgorchik tone strips, that some of them are not on the musical scale progression (they should be just like piano keys), then we will now want to adjust the strips to make them produce these even musical steps when tapped. This is very easy:
...The rule for adjustment is that the entire strip (that is the center of the strip except the wide middle strip which is made all even) is raised or lowered by scraping or sanding just the outer edge of the strip as shown. One side to raise the tone and the opposite to lower it. Just the least little bit of wood removal makes the necessary adjustment (perhaps one to three grams for the entire plate).
The blue area shows how much area is scraped to actually adjust a strip (in this case to lower the strip)..
Scrape near this edge to lower the strip tone
...You will notice that the end of the strip nearest the center bout is the side which is lightly sanded/ scraped to raise the tone of that strip.
The top plate should go from about E to E and the Back plate from about F to F (an octave higher).
... Now to review; when we are finished, the plate tap tones will be even all over (with a brisk knuckle or finger tip taps) and when we tap along the center of the Vigdorchik strips, we also hear a progressing musical scale of plate overtones from one lower bout corner diagonally across the plate in an 'S' pattern.
...The even-all-over plate tap tones will be 1 1/2 semi-tones (3/4 of a full musical tone) apart, with the back plate being higher. {on fully mature plates}. If the plates are new, then make the back plate a full tone higher (as the top plate will increase in frequency more than the back plate).
...If possible, end up with plate frequencies {after complete U.V. light exposure of the plates} that are exactly one of the Carbon 14 resonate frequencies (see separate article) and ideally ending up with a top plate frequency of 322 HZ and a back plate frequency of 353.5 HZ (your listeners will thank you for your efforts).