...I want to take you on a photo essay journey demonstrating this process on an actual instrument...

...This is my Hewlett Packard #3582A which is specifically designed to give sound spectrum analysis from a gentle tap on various parts of the instrument.

...This is a close-up view of a typical screen. A frequency range of 0 to 500 Hz (vibrations per second) is seen on the screen.. ...( The needed frequency range for violin making is 0 to 1,000Hz but the equipment range of this equipment is 0 - 25,000 Hz .)

...When reading the screen, the lowest frequency major response displayed is usually the 'heard' tap tone frequency. In this case the readout is 162 Hz. The higher frequency responses to the right of the red line represent overtones.

...I used the H-P spectrum analyzer to make and tune a set of (60) wood blocks which are (10) Hz apart in frequency and span the range from 220 Hz to 810 Hz. ...Tapping on the end of each 'sound bar' thus produces a 'wood' tap reference that I can cross-compare to the tap on the instrument, as a double check on accuracy or it can be used by itself with the instrument for 'tap tone' analysis.

...This view shows an instrument ready to analyze, and various special tappers, microphone, and sanding and scraping tools for adjustment. Notice that here I have made fingerboard and tailpiece templates to record results on.

(I want to say a special 'thank you' to Seattle, Washington area violin maker Daniel Paris who told me about the H-P #3582A and found one for me to purchase .)

...Current frequencies are measured by side tapping on fingerboard all along its length and on both sides, and all over its' top surface. ...Even carefully made violins exhibit significant frequency differences along the fingerboard surfaces. You can test this yourself by tapping along the fingerboard beside each string with the side edge of an ordinary wood pencil (unsharpened) and listening for the evenness of tap tone..

...The most important thing is that the tap tones of the top surface of the fingerboard, all along the length of the string, must be constant and exactly be matched by the string contact tap tone on the tail piece. When this is achieved, evenness, sound quality, and loudness are all optimized

...When all of the tap tones agree with in say +/- 5 Hz, with the now even fingerboard top surface, the instrument will become what it was meant to be: a fine musical instrument.

...This photo shows the strings being carefully removed.

...As each area is scraped/sanded the tap tone is constantly checked against areas which are already at the determined 'goal' frequency. ...For best results, tap down on the top surface of the fingerboard with a wooden (low-toned) pencil, using either the eraser end or the unsharpened wood end (see photo).

...Now let us suppose that the area indicated by the red arrow has the wrong tap tone. If it is too high in this area, then scrape or sand the area until its tone decreases to match surrounding areas. ...If it is too low in tone, then sand or scrape the nearest side edge of the fingerboard until the area is raised to match. ...This is the general rule, if the top surface area is too low, then scrape the nearest side of the fingerboard; if too to high in tap tone then scrape of sand the area until it is matched with surrounding areas. ...When doing this listen only for the lowest overtone and ignore the higher pitched overtones. This is very improtant (see side bar).

{...As an interesting side bar, if you listen only for the highest overtone (instead of the lowest), then adjusting is reversed: scraping down on the top surface will increase the highest overtone and scraping on the side of the fingerboard will lower the highest overtone. }

...This photo shows the small total amount of wood sawdust and shavings removed to completely acoustically tune this violin

Next, a piece of pure linen cloth is wrapped around the foam pad and the fingerboard is briskly polished. This is followed by polishing with a pure silk cloth in similar manner.

...Here we see the fingerboard, polished, tuned and ready for the violin to be re-strung and further tested. This process is repeated as necessary until the desired result {overall even tap tones and excellent playing performance} is achieved.

( Copyright 2004 (c) by David Langsather)

...There is another lower cost alterantive to having a sound analyzer. Violin enthusiast Pierre Leiba discovered this computer based sound analyzer software and it works well for tap tones on violin plates. It is currently being offered for free as beta software testing and you can download a copy after contacting the author at: http://www.sygyt.com/en/download {the default settings should get you reasonalbe results.}

Tap tone result of back plate of my Opus #10 violin

..Tap tone result of top plate my Opus #10 violin.