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Violin Bridge Adjustment (for best string sound quality)...
... Once the bridge is properly sized and fitted to your instrument, so that the string height above the fingerboard is correct and it's dimensions are at or close to professional standards; it is time to take a survey of the current bridge tap tones and then adjust to the correct tap tone ( 198 HZ for full sized violin.)
...We are going to attempt to tune the bridge so that two things are true:
(1) First; the downward tap tone is even all across the top of the bridge and this tap tone is 198 HZ, the same as the back plate of the violin.
(2) Second; the horizontal tap tone all over the front surface of the bridge (the side toward the fingerboard) will be even in all areas. (this is probably 176 HZ, same at the top plate).
..You will be able to hear when you have reached this ideal because the strings, when plucked sideways, in the center of the strings, will be unusually full and rich. We want to do fine adjustments until all four strings are equally wonderful sounding.
... If the above goals are reached, you will discover that each string, when plucked, will give a rich, wonderful, melodic, ringing tone; rather than a somewhat displeasing or uninspiring tone. As you get near your ideal bridge adjustment, some of the strings will begin to sound superior; then you know that the bridge support frequency at the string contact is correct for those strings, so now just adjust the remaining strings (by changing the tap tone of the bridge under those strings) to match the superior ones..
... Once the bridge is adjusted to be in harmony with the instrument, it should remain in proper relation from then on, enhancing your playing and audience listening enjoyment.
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...We will be using an ordinary wooden pencil (or similar tapping object) as our tapping tool. (Try to pick one out with a low toned ring when it struck against a hard object; a dull sound rather than a bright ringing tone... this will make our job of listening easier.)
... Tap down against the top of the bridge next to each string, listening to the tone (please do not 'talk to youself' in your mind, as this will interfere with your getting good results).
...Next pluck each string and listen to see if any individual strings sound especially pleasing.
..Our goal is to get all four strings to sound excellent. As soon as youu get your first string sounding excellent you are getting close to your goal for you can then use the bridge tuning for that string (top surface tap tone) as your standard for adjusting the remaining strings.
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To review this important concept:
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...All these front side areas should be the same front tap tone (on the tapered side of the bridge toward the fingerboard).
..Should there be an area that taps higher than the surrounding areas, then scrape this area until it is even in tap tone. I use a swiss army pocket knife sharpened with a diamond stone. {To get the angle of the knife blade edge correct, put two quarter coins stacked on top of each other under the thick side of the blade to set the sharpening angle. Hold the blade at this angle while sharpening blade. This can be called the 'four bit' angle (thanks to the Wood Wright Shop) for this tip.}
...At the same time as this, we want the top tap tone of the bridge to be 198HZ evenly across.
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...Next Example: The entire bridge is too low in top surface tap tone...
...One very good way to deal with this is to slightly sand the outer ends of the beam bottom section with a file or sanding stick (nail file). Sand more on the side that the top tap tone is lowest.
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...The back surface (toward tail piece)is left perfectly flat (this is usually the side with the stamped factory label). All the changes in thickness will be to the front face (that toward the fingerboard). Notice that there should be a smooth tapering of the thickness on the other (front) side, beginning with the lower cross barof wood and moving up in an arc to the top of the bridge (which should be about 1/16" wide at the string contact surface); as well as side to side.
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...One additional method to raise the tap tone of the top of the bridge is to evenly sand the sides of the bridge, from the kidney shape upward. This will raise the tap tone of the strings on that side of the bridge.
..A sandpaper nail file board works well here.
... Eventually you should be able to adjust the bridge tone so that each string has a full and rich tone. You can check this on a strung up and tuned instrument by tapping the top of the bridge beside each string . All the strings should have the same tap tone If any strings are different, check by the plucked string tones to determine which ones sound the best. and adjust the others to match the tap tone of the best sounding string. This acts as a good double check for accuracy.
...When you discover one string that has a 'heavenly' rich sound when plucked (in the center of its length); that becomes your reference for adjusting the bridge for the other strings to match its tap tone next to that string on the top of the bridge. You will be amazed at how much change in tap tone (and string sound quality) can be made with only a slight amount of material removal from the bridge!
...Now there is one more thing; tapping on each side of the string contact point on the top surface of the bridge should produce matching tap tones. If they are different, you will notice that the tap tone of directly down on the string is the average of the side of the string tap tones. We need to make that wood tap tones match each other and be at 198 HZ!
...When this stage is completed, your bridge should be in perfect adjustment for your violin, resulting in for many years of playing pleasure.

                   by David Langsather (c) 2017
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...{You can tap down from above either on top of the string or just to both sides of the string junction to the top of the bridge on a strung-up instrument (they need to match side to side).}
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(revised 10/ 2017)
Page AA_04
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...Now, for the sake of argument, let us say that your bridge is even all over on the front face in tap tone, and the downward tap across the top is even; but the top tap tone is too high a frequency (above our 198 HZ goal frequency). What to do?
...Here we assume that the bridge is not made too thick, as viewed from the side, and that the bridge dimensions are at professional measurements (see other pages for details).
. Now, to lower the overall tap tone of the bridge down to your goal frequency {which is the fundamental tap tone of the back plate, 198 HZ}, we will simply increase the depth of the "makers cut" on both sides of the bridge equally; carefully checking frequency with each small deeper cut; as the frequency changes quickly with even a tiny increase in the depth of the cut. Use a very sharp, very thin bladed knife such as and exacto knife (with a new blade) for the cut. If only one side of bridge is too high, only deepen makers cut on that side.
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..Deepen this cut to lower the vertical tap tone of the bridge on this side. Do this a small step at a time.
...However, if the tap tone of the bridge is considerably too low, then apply epoxy glue, or thick super glue, or thick violin making glue to fill in the bottom of this slot. When cured, the tap tone will be raised. Then slowly deepen as necessary to lower tap tone to meet goal tap 198 HZ..
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Downward tap tone.
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..Click here to see a summary listing of relativeTap Tone, Wood Tone, and Rub Tone relationships for a successful instrument.
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...Another way is to use a sharp knife and cut a bevel on the front of the side of the bridge that is too low in top tap tone.
...If the top tap tone is too high in a certain area. lower the top tap tone in that area by lightly filing or sanding a slight amount of material from the top surface of the bridge in that area. Just a tiny bit makes a big difference.
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