VSAJarticle2009 - Page: 7 of 14

...Removing wood from the top of the kidney shape raises the tap tone of the string above it. If all the strings are too low, then raise them all by raising the arching on the bottom side of the bridge (or just the arching under an individual string that is too low) or by slightly sanding the sides of the bridge above the kidney shapes, or by sanding both

sides of the bridge.
...Additional useful tap tuning details such as tuning the fingerboard, nut, and end pin are available at my free informational web site: www.Dalemfg.com/acousticaladjustment_0 35.htm

.. This phenomenon only occurs when the tailpiece and some areas of the fingerboard agree.
..As a general survey of an instrument's current tap tones, tap the fingerboard about half way up the neck in the center and then tap the far end of the tailpiece in the center just above the end pin, listening for the low (fundamental) tap tones. I believe that ideally the tap tone of both fingerboard and tail piece should match the back plate of the instrument, and the fingerboard tap tone can be raised or lowered as well, but that is outside the scope of this article. So assuming the fingerboard tap tone is acceptable, we want to raise or lower the tap tone of the tailpiece to match it. ..This is accomplished by removing small amounts of wood, as needed, from various parts of the tailpiece until it matches the fingerboard for all four strings. If, when playing through the scales, one (or more) of the strings is more powerful, check the tap tone of the fingerboard alongside that string with the tap tone at the far end of the tailpiece (behind that string). You will hear a close agreement. This combination of tap tones can then serve you as a guide for adjusting the rest of the tailpiece to match the other strings.

..The second topic of this article is the tuning of the tailpiece to match the fingerboard.
..Instruments with this acoustical agreement produce the maximum power possible for that instrument. When the fundamental tap tone of the fingerboard and tailpiece exactly match for each string and all along the fingerboard, then all notes are even and focused with good projection.
..A practical proof is when you discover a note that, when played, has unusual power and intensity. Carefully noting the finger position, tap that spot of the fingerboard next to the string and then immediately tap the farthest end of the tailpiece (just above the end pin) directly in line with that string on the tailpiece {See figures six and seven} listening for the lowest (fundamental) tap tone of each. I believe you will discover that there is perfect agreement.
.. Now tap the fingerboard just above and below this same spot, and you will note that on one side the tap tone is above and on the other side it is below this ideal frequency.