Violin Free Plate Mode Tuning Reprised

by Edgar B. Singleton

Originally published in American Lutherie #103, 2010



In the early stages of violin building, the outline of the top and back plates are established, as is the contour of the outside surfaces. Wood is removed from the underside of each plate until the thickness of the plate is a millimeter or so thicker than expected to be in the final form. The f-holes are cut; the bass bar and purfling are installed. The time has then come to graduate the plates, i.e., regulate the thickness of the plates in an attempt to assure that the finished violin will have all of the desired characteristics. Some builders “graduate to thickness” by carefully copying thickness measurements from important old violins. They listen to the pitches of tap tones and have learned ways to adjust these pitches. They have also learned to bend and twist the plates in their hands with the goal of assessing elastic properties, using experience to relate these “felt” properties to the finished violin.¹ These processes involve as much art as science and require many years of carefully evaluated experience. This experience is very difficult to articulate to the novice builder.

One process associated with graduating the plates that is related to tap tones is referred to as “free plate mode tuning.”^{2 3 4 5} The following exposition is intended to help instrument builders, familiar with the material contained in the above references, understand the basis of free plate mode tuning as it is based on some simple physics and to provide a technique to fine tune each mode (tap tone) individually. The purpose of this paper is to give the builder a new basis on which to visualize where, and to understand why, to remove wood if one wishes to tune the free plates of a violin.