Bueno, con respecto a eso de afinar la tapa para llegar a una resonancia específica, Cumpiano dice que es un cuento. Esto es lo que dice textualmente en su website (
www.cumpiano.com):
"How DO I tap tune my guitars?
Sorry to tantalyze my readers, but my building technique doesn't include "component tuning." My experience of thirty five years has led me to the conclusion that "tuning" the sound of a guitar is an illusion and a chimera, and those who publicly advocate that they can accurately control the response of a guitar by responding to noises derived from tapping parts of it, are simply seducing the innocent, or at best, self-deluded.
The short discussion in my book about tapping the soundboard while reducing the thickness of the soundboard was, admittedly, my passing on in an uncritical way, the vague mumbo-jumbo that I was fed by older builders during my years at the guitarmaking factory in the early 70's, when I first learned guitarmaking. The illusion persisted until I concluded, sometime after I wrote the book, that it was, well, an illusion...not to say, a crock.
Now, twenty years after writing the book, I have a different point of view. It's summarized by the following entry into Newsletter 19:
You heard it here first: "Tap-tuning" has been oversold. Let's put it into perspective.
When I was learning guitarmaking, I went through what you're going through: I had HEARD about something called tap tuning and was mystified and tantalyzed. I presumed that it held THE secret for easily-replicable, world-class results. I actually thought that the alchemy of guitarmaking was somehow locked inside this arcane act of wizardry called "tuning" the top, that it was something that only the select and most sensitive few knew about, and that they weren't going to tell me, so I would somehow have to learn it myself.
Builders, alas, often do things on guitars which they really don't know WHY their doing it, but they do it because they were taught to do what the teacher did, and they're afraid if they stopped doing it, the nice sounds they usually get will go away. So they keep doing it. Then, when you ask them why they do it, they are all too happy to MAKE UP vague, fanciful, jargon-laden accounts which will leave an impression that they know exactly why they're doing it in minute detail, and by implication demonstrate that they can somehow successfully manipulate all these invisible sonic phenomena on the guitar with ease. Luthiers usually won't stop you from believing that they are wizards. This is most painfully obvious in the realm of "tap tones."
Yes, I do "tap" a top to derive some rudimentary information about its anatomy. What you hear does give you some feedback clues which is useful and helpful. The "tuning" part is what is so misleading to beginners. At some point (most often toward the end of the process) many builders attempt to make some final changes in the anatomy of the soundbox, which the builder believes (I've selected this word carefully
believes, is exercising some control over the final results. Both, skillful experts and deluded fools, equally, scrape here and there, tap, press, reach inside, remove a little on the back braces, on the top braces, and then at some point say THERE. It's just right.
Then there are other builders, masterful experts and deluded fools alike that DON'T. They believe that they're making all the crucial decisions in the INITIAL stages of the construction: materials selection, materials dimensioning, design: that is all they need to achieve the desired results.
My approach today seeks to achieve a balance between a guitar's structure and it's compliance--factors usually in opposition to each other. I have come to rely largely on visual cues--not auditory ones--displayed by the actual materials at hand and an evolved sense of how to reduce the guitar's structure to an optimum state. Thus, the beauty of the vibrating string can be realized with as little impediment as is structurally possible--given the need for the guitar not to distort under string tension over time. This is a long way of saying that if you want to learn how to "tune" the soundbox by the sounds the individual parts make during assembly, well... please inquire elsewhere."
Habrá que atender más a la práctica y menos a la teoría esotérica...