Violin Rub Tones and how to use them to select violin wood parts...
(updated: 7/23/2014)
...My name is David Langsather, a violin maker and researcher living in Salem, Oregon USA. This summer (2008), I believe I have isolated a feature of wood that I am naming "rub tones" which appears to have a significant role in selecting proper pieces of wood (and wood fittings) to make a stringed instrument sound better.
...Encouraging results from initial experimentation as well as examination of several excellent performing instruments and the results of several experiments changing three violins and a viola to more closely approach uniform "rub tone' in their various parts, has convinced me that this may be an important component of producing the excellent sounding instruments we are all seeking to make.{7/2010: listen to actual sound: see Opus #24 info.}
...This technique can be used to identify which parts of an instrument are not working with the rest of the instrument so that they can be replaced. It can be an important tool in deciding which instrument to purchase in the first place. Most importantly, I imagine that this technique should be the initial guide in selecting which pieces of wood are chosen to be joined into a new instrument; perhaps determining whether the instrument under construction will ever amount to something special to those who will hear it played.
...I believe that comparing "rub tones" will also become the first step in selecting the proper bow for your violin, viola, cello, or double bass in the future .
...In summary, wood components of the same rub tone, sound good together and any thing less than accurate "rub tone" agreement lessens the sound quality of the instrument when completed. The internal parts which can not be easily changed after construction such as ribs, corner and end blocks, top and back plates, the glue liner strips, and neck wood especially need this guide during construction as they are difficult to replace later..
...First, let us define "Rub Tones": Webster's dictionary defines 'rub' as: (vb) "to move along the surface of a body with pressure". For this application, I suggest you stroke a piece of wood with the long direction of its grain, touching it lightly. A rapid stroke will produce this characteristic 'hiss' sound. It is best to use a low toned soft wood stick (such as a low toned and unsharpened wooden pencil, although almost anything can be used including the tip of your finger or fingernail
..This 'rub tone' will vary with different similar wood boards (such as in a table top or wood floor) and there is a wide variety of 'rub tones' in identically make violin parts such as pegs, tail pieces, fingerboards, saddles, nuts, and fingerboards. Even wood from the same tree may exhibit a variety of 'rub tones' in different parts of the tree.
...At this point I ask the reader to select a piece of soft wood, or your fingernail or really almost any object that will not scratch the surface of the subject piece of wood and lightly and rapidly stroke the surface of some wood samples, with the grain, listening for this characteristic 'hiss' or 'rub tone'.
...I suspect that this rub tone correlates to the speed of sound in the particular wood piece being tested. It is a permanent characteristic of that piece of wood and will not change with changing the size of the piece of wood. Wood with a higher 'rub tone' (more lively tone) would probably transmit sound at a greater speed than a similar piece with a lower (more muted) 'rub tone'.
...From what I have seen so far, it probably is not so important whether the rub tone of the violin building materials is higher or lower, but rather as long as all the wooden parts exhiblt the same 'rub tone' characteristic, then an excellent instrument is potentially possible. Said another way, if the 'rub tones' vary widely thoughout the instrument, its future potential is reduced.