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I am no pro, and if fact a very " simple guy"?!!! I am cleaning up the top on my tenth guitar, which is to be my second 12 string, so I don't have a lot of soundboards under my belt, my hearing , although good , is not what it used to be , darn ringing!!!...I have Kent Everetts dvd on voicing, which has a ton of good info on it..but , and maybe it's me, but I still don't get it. I have a good understanding of bracing and the effects of mass on tone, for instance light bracing on fingerstyle to bring out mids and heavier bracing on larger guitars to sound more , bassier, and to keep from overdriving a top like a 12 string. Right now I have 3 tops in front of me, a light L-00..a OM , and this 12 string top. I have spent a lot of time on each and they all sound good ...but different!!!!! Like wood!!!
So I was hoping to get some thoughts on the subject, is this all it's cracked up to be, I know there are some schools of thought that its all "voodoo" and others who swear by it..

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MK5acoustics.com

I'm no expert on this either.
As far as tuning it to a note goes though, I don't think there is much to this because the tap tone is going to be changing all the way through the build process. So, say you get it to whatever pitch you want, once the sides are on, its gonna be different. And then once the bridge is on..same thing...and then once the finish is on, its going to be different again. I generally voice my soundboards by just working the board until it seems to, I'll say, "open up(?)"

Oh.. Sure... Easy topic.... Kinda like how Politics is an easy topic too.... so long as you agree with me

Any way.. First question... What exactly do you mean by "Tap tuning"?
Everyone does something that we call "Tap Tuning".... but everyone out there means something totally different by it....

Let's go through a couple possibilities....
"Bonk and listen" - literally, rapping with a finger or knuckle and just listening to the changes that happen in sound as you make changes to the wood....

Siminoff's tap tuning - where you use a piano hammer and a strobe tuner to tap the individual braces, and then adjust the braces until they each read some frequency, but the same adjustments aren't done on the finished top...

Classical guitar top tuning - where they "Tune" the resonant pitch of the finished soundboard to some note

Chladni pattern testing/tuning like Al Carruth does (Which measures resonant frequencies and then you adjust them to suit yourself)

Here's the last thing.... What's actually wrong with the way you are doing it now? Are you unsatisfied with your instruments? Do you feel like the method you use to gage the state of the top during voicing is lacking? There's no good reason to only limit yourself to how the wood "Taps"... Why not use your other senses to also get a feeling of what's going on..... I have seen luthiers flex the wood in different directions and different places to get an idea of how stiff or loose it is... I have seen folks rub on the wood and listen to the noise it makes when rubbing on the wood.... Other people dump a bunch of sawdust on it and bonk it.... Other folks do none of this sort of thing... They just build and don't worry about it....

You get the idea....

Yes, a can of worms this one.

John raises some good points, amongst which (paraphrasing) is “Why would you want to? which leads to my question “Does it make a difference?”

The answer in most cases is probably not. I say that because I haven’t been able to distinguish a body of guitars out there that are somehow significantly different, where a causal factor is identified as “tap tuning”. If there was, and the difference was positive, everyone would be climbing on board and there would be no need for this discussion.

However, as one makes louder and more sensitive guitars there comes a point where a stack of new problems arises, which don’t present themselves when making more conventional instruments. Keeping them playing in tune over the fretboard, avoiding “dead” notes, and avoiding an overly raucous or percussive sound become major issues and some approach has to be found for addressing those problems. Tap tuning won’t address them as its exponents struggle to explain what it is they’re trying to achieve. Cumpiano’s discussion is interesting (though there’s a lot further down the page that I can’t agree with) http://www.cumpiano.com/Home/Newsletters/Issues/twentythree.htm . He concludes “So I don't worry much about "tap tuning"……It's a fool's errand.”

So what do you do? Well, modal tuning provides an answer. It’s an extension of John’s “Classical guitar top tuning…” where certain resonant frequencies of the finished guitar are tuned to specific values and relationships. They are tuned away from scale tones (so you don’t get a scale tone corresponding to a modal resonance, which would give you a clunky sound on that note) and you don’t place resonances an octave apart (because that gives an admittance peak on two harmonics of that note, delivering another clunker). Then you have to attend to the intonation, tune the back, etc. and the list goes on. Which is why most builders work within the recognised norms and “main street shop” guitars have remained much the same for most of the last ~100 years.

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Trevor Gore, Luthier. Australian hand made acoustic guitars, classical guitars; custom guitar design and build; guitar design instruction.

http://www.goreguitars.com.au

Like i said before (don't kill me now) its about having the right feel for the whole picture. anyone can build a guitar ! might be looking like crap, but its a guitar. To build a good looking and sounding guitar is another issue. So tap tuning "to me" is just a part of the whole thing. Try several Bourgeois guitars wish Dana Tap tunes, and you'll hear that when done right, there´s a big difference compared to listen to a bunch of martin, taylor gibson guitars. but then again its just 1 part of the whole pic and to get it all right we need to understand and execute all things correct, like brace hight, width, stiffness of braces, tops, sides, backs.
When having a talent or to not upset to many , having enough experience and chops for guitar building then Tap tuning in all its forms are essential. Just like a drummer taps the skin on the drum adjusting the pitch until it "sounds right" the better question would be- what sounds right ? smallman, chandli, Bourgeois ? etc. still, they all sounds good depending on taste. Wow philosophy
If not tap tuning what would you use ? just measurements ? to me I see it as each piece of wood has its own "perfect criteria" therefor I need to listen/tap each piece, plane it, listen plane it, listen until hearing its full potential. if just building by measurements then how would you know the stiffness of each piece of wood. its all a mix of measurements flexing, Tapping to get a similar result on each guitar. I am not there yet although getting closer.. .

Lars

Though it really applies more to electrics, I generally prefer "Oigun's" (from the TDPRI forum) method of forking the instrument.
http://www.tdpri.com/forum/3122385-post17.html

Just curious, which specific points in the Cumpiano blog do you disagree with, in fact CAN'T agree with, and why? Not being contentious here, mind you, I'm just curious.

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Old growth, shmold growth!

The other day I was trying a bunch of $2k guitars at the store, and one really stood out. It was a Breedlove, it seemed more balanced, and didn't have that annoying low mid hump. One thing that set it apart was that the top and back seemed to be tuned a fifth apart, where the others were tuned about a third apart. Made me think I might want to shoot for this interval. The Breedlove had that bridge doctor thing on it, maybe that is part of the equation.

OK.

First up, I generally agree with WRC’s assessment of Siminoff’s tap tuning method. When I first read that stuff it made my teeth curl, and it still does.

WRC then follows with 6 “considerations” for tonal consistency, which I’ll just refer to by his numbers.

1) This is about the selection of wood by “seeing and feeling”. Possible to do if your suppliers are less than a continent away! Yes, you can observe quartering and runout, grain line density etc. which are indicators of a certain quality of wood. Personally, I have tapped a lot of rough wood and correlated that to log. dec. (damping or Q tests) and I can pick high Q wood quite consistently. What I can’t do, which is at least as important, is pick the resulting mass of the soundboard when it is incorporated into a finished guitar. This is a function of its density and stiffness. However, they both move together (less dense correlates with less stiff). Good, for me, means a low mass soundboard for a target vibrational performance and I can only figure out which boards are going to produce low mass soundboards by measuring density and Young’s modulus and doing the appropriate calculations. Having measured hundreds of boards, I still can’t pick it by flexing etc.. I have to do the calculations. So I can’t agree that you can make a good assessment of a board’s future performance by just “seeing and feeling”.

2) This says that success is derived from building to precise linear dimensions. I’m sorry, but I can’t live with that one. Wood is a very variable material. Even highly select tonewoods can easily vary by a factor of two in key material properties like Young’s modulus. You can read about that here:

http://scitation.aip.org/getpdf/servlet/GetPDFServlet?filetype=pdf&id=PMARCW000012000001035001000001&idtype=cvips&prog=normal

If you don’t know the stiffness and density of your wood (and how to accommodate its variability) you are guaranteeing a variable acoustical outcome, because, if you’re building to linear dimensions, you’re building to a mechanical tolerance not an acoustical one.

3) I can live with most of this, but take exception to the last sentence. For example, I routinely calculate to have my guitar backs (for live back instruments) come out a little stiffer than target. Then on the assembled guitar I trim one brace in one place to get the stiffness response I want. I find that I have to hit this target fairly accurately, more accurately than I can predict by “dead reckoning”, so I trim in after I’m done with everything else.

4) Agreed. But WRC’s comments are actually inconsistent with his points 2) and 5). He recommends building to tight dimensional tolerances, not structural criteria.

5) Problematic for the reasons given in 2). Even if you build a copy of an instrument to identical dimensions you most assuredly won’t get an instrument that sounds identical, or even anything like. Then what do you do? Build to dimensions that are even more identical? French alludes to this in his paper in American Lutherie #90, Summer 2007, where he tested 30-odd Taylor guitars, which are probably built as identically as guitars are likely to be built (seeing as robots don’t deal with dimensional variation very well). The main top resonance spanned a 20 Hz range, 169Hz to 189Hz. There is no way the ones at either end of the range could sound similar to each other with that level of acoustical variation; but that’s my assertion based on my experience, not a point that French makes.

6) This can be interpreted in a few ways. I have issues with “dimensional accuracy” as above, but when interpreted as the accuracy of fit of components, precision of gluelines, precision of set up etc., I agree entirely; but elsewhere I draw a distinction between the playability and musicality of an instrument. WRC infers that these two things are largely the same, but they’re not.

Sorry about the long answer, but you did ask!

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Trevor Gore, Luthier. Australian hand made acoustic guitars, classical guitars; custom guitar design and build; guitar design instruction.

http://www.goreguitars.com.au

Long answers are good. I must point out though, it seems to me, that you in fact are also picking woods by seeing and feeling, you've simply added two more criteria, a measurement of Young's Modulous/stiffness to density ratio. I would call that seeing, as you have to calculate and "see" the result, and have also added a target vibrational component. Your criteria is simply more strict. This is not a criticism.

Second, I don't know of any builder who claims that they can make all their guitars sound the same. That's not the point. Cumpiano doesn't say all his guitars sound the same, so I don't understand your response number 5. I went to Cumpiano's shop and played through about 20 of his guitars that were made by him during his tutorials, they all sounded great in my opinion. I am an objective person, too, so I wasn't sitting there in awe of William and thinking his guitars sounded great just because he made them. I wanted as accurate an assessment of his methodology correlated with his results as possible, for purposes of evaluating the BS factor. So I would have to agree that based on his results, his methodology is consistent. Also, I think you misunderstand what he means, I don't believe that Cumpiano intended to say that playability and musicality of the instrument are the same thing. I think he believes that they are both the result of suberb craftsmanship, but I'm sure most luthiers would agree in that regard.

I realize you aren't criticizing WC,so don't think I'm trying to defend him to you, as I realize that is not necessary. This is a thread about thoughts on tap tuning, and WC's name came up. I personally think that his methodology is incompletely understood as simply building to dimensions only. The rest of this reply is provided simply for information to add to the discussion, and represents my understanding of WC's methodology, I suggest if anybody wants to know further, they e-mail William directly to verify the accuracy of what I present.

Part of our discussion in his shop centered on material selection. The stiffness and weight is very important, as the vibrating string must overcome the inertia of the static structure to resonate and produce sound, a heavier top requires more input from the string, yet a lighter top must still be strong enough to resist the tension of the strings adequately, so the weight is very important. A stiffer top can be made thinner to reduce the weight, and a lighter weight top can be left thicker to make up for the stiffness, so there is room to adjust, based on experience. Another discussion dealt with how strings interface with the soundbox at the headstock and bridge, to understand how guitars produce sound, and how the materials can affect that. He pointed out that guitars are not percussion instruments in the same sense that drums are, nor are they sympathetic resonators of sound pressure waves through the air, so tapping on them and resonating them with speakers doesn't really give you direct information about how the strings resonate the top. To understand that, you have to slow the string down and observe the action of the string/saddle interface, and build accordingly to get the most response out of the instrument. My understanding of his methodology is that the string holds an amount of tension. As the string swings back and forth in it's vibrational arc, the tension increases during the outer swing, returns to neutral, then swings the opposite direction. Not only that, but there are several sets and subsets of vibrations going on throughout the cycle. Each vibration of all the cycles tugs at the saddle, rocking it back and forth, and imparting energy into the top.

What this means, is that, in his view, the way to make the top the most responsive, is to built the entirety of the guitar to a minimally adequate level of structural integrity, such that the structure of the guitar is able to hold the static tension of the string, and NO MORE. Thus, the top can respond to the barest increase in string tension, imparted by the slightest touch to the smallest string. Since the tensions of the strings and the structural properties of woods can be measured, a minimally adequate structure scheme can be derived, and refined through trial and error to account for variances in material. Tap tuning, Chladni modes, flexing the wood, these are all ways that different luthiers use to arrive at a minimally adequate structure. Thus, in the final analysis, his tight dimensional requirements, are in fact STRUCTURAL CRITERIA, not separate, as you say in point 4. So, based on his principles of construction, tap tuning and chladni modes would be extra unnecesary steps for him, as he has, through trial and error, derived a formulation of material selection and construction methodology that works for him and pleases his sense of sonority. I also must point out that material selection is key (as you well know since you have such strict criteria for selecting your materials) and figures very heavily into the method. We discussed how to select, split, and shape braces for optimal strength to weight ratios and structural integrity. In his view a guitar made with substandard materials and made to his specifications would likely fail in some aspect at some point.

So his methodolgy involves more than just grabbing material, sizing it, and gluing it together with suberb craftsmanship. The structure of the material, the weight, the stiffness, all are taken into account to produce the final instrument.

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Old growth, shmold growth!

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Old growth, shmold growth!

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Old growth, shmold growth!

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Old growth, shmold growth!

The inimitable quadruple post!

How the........

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Old growth, shmold growth!

I think it would be easy enough to get into an argument about what Cumpiano said or didn't say.... The sense I got was that he believes that experience is the best teacher.... and that the 2nd piece was that believing that the brace shaving was the only thing that effects the "Voicing" of the top just shows inexperience or maybe just naivete....

My own experience is that you can pretty well undo almost everything you did right on a top by doing things wrong on the bridge, the saddle, and the top finish.... You can leave a whole lot on the table by using strings that are too light for the structure, or badly mismatching the back and sides structure to that of the top.... or just poorly choosing the wood for the planned instrument - like say using a really hard, dense, stiff piece of spruce topwood on a very lightly built classical...

Back to the OP's question... Maybe an interesting thing to do would be to try out some of the other methods of "Voicing" to learn from the experience... Maybe try measuring Chladni patterns or Modal frequencies to at least get an idea of where your instruments shake out.... Perhaps "Voice" a top to where you think it's good - then try to go a little further by checking chladni patterns... or maybe just experiment with making it a bit thinner in the center or at the edges.... Who knows....

Thanks

I took Cumpiano's class a while back, I'm just trying to clarify his methodology a little, which I think is frequently misunderstood. People can make up their own minds.

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Old growth, shmold growth!

Point taken, John. I was asked to comment on WRC’s blog, not what he might be saying in his building class or whatever! However, I feel a few things do require some tidy up though…

Yes, when I can source wood here I am picking wood at the lumber yard by “seeing and feeling” because I can’t measure it without working it (which means buying it first). I think calling the measurement of Young’s modulus and density “seeing” is stretching the definition of seeing a little! The whole point of the measurement approach is that it enables one to make a consistent guitar from woods of variable properties, and wood is very variable. It means your top thicknesses (for example) are always different in a systematic way to account for the differing properties of the wood. Quoting WRC “Success and consistency is derived from reducing the thickness of the guitar’s top, back and sides to a set of precise dimensions that have been learned over time to be the most appropriate”. If you have the luxury of being able to select wood (by whatever means) such that it always has very similar material properties, that’s fine, but, I would suggest, not a very realistic proposition for most people. The measurement approach that I use means that the spectrum of acceptable wood becomes very much larger, which has to be a good thing in this day and age.


No worries, I’ll elaborate:
Cumpiano says “However, the great majority of professional builders I've inquired from, seem to agree that tonal success and consistency is, rather, derived from far more straightforward, if not equally elusive, considerations”.

Consideration #5 is:

“Success and consistency is eventually derived by starting from the beginning by duplicating as closely as possible the dimensions and plate thicknesses of specific admired guitars, guitars which serve as models and a starting-off point in further developing a personal building style”.

Cumpiano is talking about achieving tonal consistency. Sure, he doesn’t say all his guitars sound the same. My point is that tonal consistency (which, at least, must mean a certain similarity of sound, more so as the bar is raised) will not be achieved by building to close dimensional tolerances unless the materials and build processes are identical (and how would you know what the wood qualities were of a “reference” guitar that you’re copying?). The point in quoting the French/Taylor work was that the latter was satisfied (build process consistency) but not the former (material properties – even though Bob is pretty thoughtful about how he selects his wood).

I was commenting (at your request) on a fairly literal interpretation of his passage on tap tuning, rather than anything else WRC might have said or done.

One more thing:
This is essentially Simonoff’s published description of how a string drives a guitar top. Fletcher and Rossing (Physics of Musical Instruments) show that in fact it is the transverse string force (rather than the tension change force described above) which largely drives a guitar top to produce sound.

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Trevor Gore, Luthier. Australian hand made acoustic guitars, classical guitars; custom guitar design and build; guitar design instruction.

http://www.goreguitars.com.au

Basically, I get worried when threads like this one steer off into the weeds about what some famous luthier meant when he said such and such... It seems like about 75% of the threads about tap tuning end up getting derailed by discussions about Cumpiano's opinions and newsletter/blog posts....

But since it's already steering off into the weeds... I will help with my own contribution....

I suppose the part that I finally came to understand is that when people don't communicate the "Secret" of how to voice a guitar in a way that seems correct... It's not because of some malice or wanting to hold on to secrets.... The actual explanation is far less mystical and actually pretty boring after all....

It has to do with the way the brain figures out how to do things and the parts of the brain that figure it out.....

Say for example - how do you recognize your mother out of a large crowd? Say I asked you to describe your mother.... Likely the description you give would fit about 10% of all women on the earth...... so maybe 1-billion people *Could* be your mother from your specific description - but it's really only that one..... You can tell her out of a crowd when she is turned around facing away from you... Her hair could be styled differently than usual.... Clothing could be very different, etc... but you would still know.... How do you know?

You know because you know... There's a part of your brain that understands which one is the right Mom.... BUT... That part of your brain that understands specifically how to recognize Mom isn't the part of your brain which makes words.....

You find that it's the same for hitting a baseball or cooking a fried egg or grilling a hamburger or recognizing the flavor of Coke vs generic cola or even voicing a top..... Some part of your brain recognizes the signals and says "Yep"... You get an urge that it's now fine..... Try to articulate how you know it's fine - and with most people it makes no sense....

Trevor can probably attest to seeing this after both working with Luthiers and doing the computer modelling, FEA, etc.... At some point - the Master Luthier says "That's about right"... Ask him what he is looking for and how he specifically knows how to adjust this or that and the most of the time, the words are more or less gibberish - and may even mess up his process.... because it's not the Make Sentences part of the brain that does the tuning.... Likely Trevor's research has pointed towards things that the brain senses when it gets closer and closer to "Right"....

It turns out that when Torres famously told people that he could not tell them how he voiced a top - it was his fingers communicating with his brain that did it... He was actually correct... He wasn't telling lies or trying to hide some deep secret from competitors... He simply recognized that he couldn't explain how he knew when it was right... but he knew it was right....

Within this understanding - Cumpiano's answer makes more sense.... It's an explanation that you shouldn't try to swamp your brain with limitless options it will take forever to figure out.... Figure out what you do well - and then limit the choices of incoming raw materials and guitar specifications to narrow the possibilities from "Limitless" to "Something my brain can deal with".... Maybe come to to terms that there is sufficient wood in the world that you don't have to use every single piece of wood that shows up at the doorstep - that it's OK to sort out what you want and sell off the rest.... Maybe pick 3 or 5 guitar styles and focus on those rather than trying to make Martin + Gibson + Tonk brother + Torres + Ramirez + Hauser's entire catalog of instruments.... It helps us move through the "Jack of all trades, master of none" problem....

Thanks

How is this thread getting de-railed? This is a good discussion. Trevor has some good responses and seems like a good brain to pick.

My understanding of "consistency" means "consistently good", not "consistently the same". However, all of Cumpiano's guitars had good tone. The highs were clear and responsive at all times, and the bass was full but not muddy, even though the actual character of each guitar was slightly different. I would call that consistent. He achieves this with no component tuning, so the relevance to the OP is that no, tap tuning is not necessary.

As far as the transverse wave goes, that's simply a description of how a string vibrates, the waveforms travel longitudinally across the string perpendicular to the top, starting in opposite directions from where the string is plucked. From what I felt in the experiment that we did, is that the string does in fact increase and decrease in tension as the waveforms travel back and forth across the string and interract with each other. Are you saying that because a wave is traveling back and forth across the string that the tension no longer increases and decreases across the string? If so, I think that is demonstrably false, and if not, then the saddle is still being tugged by the string. Seems to me that describing the wave as transverse is simply a more detailed description of the string wave.

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Old growth, shmold growth!

If a builder can achieve a higher level of tonal consistency / "consistently the ~same", then the builder can also more accurately hit a tonal target for a specific customer.

That said, this discussion reminds me firing pottery glazes: Some potters like the surprise of seeing how a glaze will come out of the kiln--letting the "kiln gods" make varieties of beauty. Some potters like more control on the process so they get more of what they intended. Both make nice pots. (With pottery and guitars, I happen to be about 30-70 in each camp.)

On transverse and longitudinal string forces, I was just reading this in Fletcher & Rossing... for a high E nylon string, they say the long force pulses are typically much smaller (~1/40) than the transverse pulses, though the difference decreases for loud playing (p 242 and 253). I haven't run the numbers for a steel string yet -- anyone done that?
http://books.google.com/books?id=9CRSRY ... &q&f=false

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David Malicky

THIXOTROPIC!!!!!!

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Old growth, shmold growth!

[quote="theguitarwhisperer
My understanding of "consistency" means "consistently good", not "consistently the same". However, all of Cumpiano's guitars had good tone. The highs were clear and responsive at all times, and the bass was full but not muddy, even though the actual character of each guitar was slightly different. I would call that consistent. He achieves this with no component tuning, so the relevance to the OP is that no, tap tuning is not necessary.
.[/quote]

I think where Trevor is aiming with his methodology is not to have his guitars sounding "Good", rather achieving higher levels of response than standard, high harmonic content, with even response and no dead areas on the fretboard.
To do this he has found that he needs to have a highly mobile soundboard, a responsive live back, and specific resonances from the body, top, and back.
His approach includes testing materials, both for suitability and to determine plate thickness, and adjustment of the finished guitar to achieve the target resonances.
It's about not accepting that most of your guitars will sound good while the occasional one will sound excellent.

So i should change the pfrase from "consistently good" to "consistently phenomenal". That's easy to do!

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Old growth, shmold growth!

I ran the numbers for a full steel string set and a full nylon string set for a variety of pluck amplitudes. The details are where you'd expect, but summarising, for nylon strings the tension change force is much smaller than the transverse wave force, as you note. However, the ratio between the two is smaller for steel strings (~4:1 for a 3mm pluck).



The alternating force on a string termination can be resolved into two components, one parallel to the string at rest and the other transverse to it. The transverse force equals the string tension multiplied by the sine of the deflection angle; the tension change force is equal to the tension change (which is a function of the string's longitudinal stiffness and its deflected shape) multiplied by the cosine of the deflection angle. On a guitar, the former is always significantly larger. This is not just opinion. The physicists worked it out hundreds of years ago but it's been misinterpreted by luthiers for a similar time span. Start with the one dimensional wave equation (you'll find that in any decent physics book, or on the web) and work on from there. Or you could just look it up in that very comprehensive book!

Strings warrant another thread, if people want to continue further.

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Trevor Gore, Luthier. Australian hand made acoustic guitars, classical guitars; custom guitar design and build; guitar design instruction.

http://www.goreguitars.com.au