Friday, May 21, 2010

Tap Tone

I read an article the other day in which the author stated that tap tuning was an inadequate method for building a good sounding acoustic instrument and that measurements and placement of bracing was a better standard. He went on to say that each luthier that was asked how they tap tuned could not give an exact description of what they were looking for and therefore it can not be a good method. So I thought I would blog my method.

I believe all of the above to be true for the new builder, but I've found in the years that I've been building that there definite benefits to tapping tops and backs before bracing, after bracing, again after carving the braces, after the top is on the sides, and finally after the box is complete. At first its awkward. You must learn how to hold the plates properly so not to fully impede the vibration. Then you have to learn where they resonant which I've found to be generally the center of the lower bout. Finally you have to learn how to tap it and what to listen for. The main thing that I listen for is the pitch and duration of the tone that the plate produces. For beginners getting the plate to a roughed in thickness and then tapping it periodically through the planing process helps to establish the changes that a plate goes through when it gets thinner.

Once you have a baseline you can start using it to change the overall resonance of the plates. After I brace a top or back I tap it and notice the difference from before it was braced. I then carve the braces a little at a time until I find a nice ringing sustaining tap tone. I generally am not concerned with exact pitches. For example I do not tune a plate to a specific pitch. Although I've found that for certain builds that making the top have a lower pitch did make it sound bigger with fuller bass response, but I couldn't tell you what the exact pitch was. I do strive to keep the top and back plate different pitches from one another to avoid common problems that can occur when that happens. Once the box is together I tap the top then the back in the center of the lower bout and listen through the sound hole to finalize my mental data. All of this doesn't start paying off for many instruments down the line, but it has payed off in the long haul for me and I think the catalog of tap tones has helped me build better and better instruments.

This is the main concern I believe the author of the article has with tap tuning. It is not a text book method. It is a long process that is general in one sense but in another completely dependent upon the individual luthier's ear. It only serves the purpose of allowing a luthier to shape the tonal characteristics of a guitar while they are building it.

The reason I think this method is far superior to measurement alone is that each piece of wood is different. One piece of spruce may ring and sustain while being on the thicker side and another on the thinner side. Then add the brace material, the neck, and the back and sides all being different pieces and types of wood. Wood is organic and therefore so should building be. I do not discount measurement as valuable tool. I use it because it works for the majority of things. It also keeps one from going to far because there are certain limits to how thin a plate can get. But when it comes to making the final touches I let my ear be the judge.

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