The correct tuning of instrument backs and soundboards is a very time-consuming activity. After all these years I do am able to construct an instrument quickly and efficiently, but when it comes to lay down the timbre and the mechanical resistance of the board, it is impossible to estimate the total number of working hours. Some pieces of wood achieve the right tonal responses sooner than others. Every specific arching has its own properties regarding the dosage of fundamental tones and overtones. The flat plates will sound deeper than the curved ones; the coarse a lot lower than the narrow grained. This means that, since the constructor aims for an ideal acoustic image, he has to meet, for every piece of wood, the challenge of reacting as open minded as possible to the fundamental tones the wood displays.
At the start, you can cut out thick wood shavings with a plane or a gouge, but gradually, you'll have to switch over to a more delicate plane and finally to scrapers.
First one can use thickness meters, but those will systematically be replaced by the concentrated manual bending and above all by the subtle tapping of the wood. To determinate where it is best to take away wood, I also use a tone generator. It can, if necessary, relief a doubt about what to do.
I also keep to copying the different vibrational patterns before I glue the instrument together. This way, I was able to make the arching of the soundboards and instrument backs grow into what they are today.
After the partial mounting, I check the wood on its technical resistance in order to lay down the bridge heights. By doing this, it is possible to avoid that the instrument sounds good the first year, but suffers from the high string tension afterwards.
When the instrument has been completely mounted and strung up, I record a few notes on the computer. In the basses as well as in the high pitches, an analysis of the frequency can give a resolution about the period of time during which the fundamental tones and the overtones will gain and lose strength.
If your working method is similar, or if you believe you can impart something, feel free to contact me, maybe we can exchange some experiences.
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