November 3, 2011

The guitar is about many things: craftsmanship, commerce, history, tradition, entertainment, science, wood and gut and a few other things, physics, acoustics, skill, artistry in design and ornamentation, music, marketing and merchandising, magic, etc. Mostly, the guitar is supposed to be about sound. But that thing is the hardest of all the things on this list to pin down and get a measure of.

Sound is air molecules hitting and exciting our ear drums, pure and simple. But there’s no magic at all in this objective description. The magic in musical sound all happens subjectively, in the brain and in how it’s able (through innate ability, training, and acculturation) to processes the neural impulses being sent in from the ear. In this regard sound is very much like food and wine, where the magic happens in one’s own mouth, tongue, palate, nose, eyes, as well as in one’s brain. While many of us report that we “like” this or that sound or wine or food — the fact is that many of us hold these preferences because we’ve learned that we should have them, without ever knowing whether we have any authentic preferences that are different. So when it comes to guitar sound, I’m big on listening and really paying attention. And I recommend it to everyone.

Guitar sound is complex. Good sound is, by definition, sound that pleases the listener — whether he understands anything about the sound or not. A guitar can have any combination or quality of: bass, treble, midrange, resonance, timbre, definition, sustain, projection, dynamic range, warmth, volume, percussiveness, tonal bloom, note shape, harmonics, sweetness, clarity (or lack of it), tonal rise and decay time, cutting power, spareness, evenness of response, brittleness, directionality, separation, brilliance, dryness of tone, tinnyness, tonal darkness or lightness, and/or cleanness of tone. So, unless you have a really sophisticated and practiced ear, it won’t work to evaluate a guitar’s sound by listening to someone play a whole piece of music on it. That amount of information overwhelms the average ear within the first eight or ten bars of the song.

However, there is a way of coming to grips with sound that I stumbled on a few years ago. It is so simple that no one ever thinks of it: that is, really listening to the simplest sounds the guitar can make — and doing it in a quiet place. It’s very much like tasting food or sipping a wine; one does it slowly and without distractions, in order to get a reliable sense of their flavors, textures, sweetness, spicyness, and overall pleasingness. Let me explain what I mean, and my own method; it’ll help you next time you are shopping for a guitar to buy.

What I do (among other things) is to sit down, tune the guitar, and just play a chord. I play it slowly so that I can hear each note separately. And I listen until the sound dies away. I do this more than once. A simple chord can give one a lot of information, especially if one takes one’s time at this. It can also be useful to listen to a second guitar, to compare against. The thing is: the voice of the guitar is the voice of the guitar regardless of what’s being played. But playing a chord, or a few notes, will give you all the information that playing an entire song can give you — without your senses being clogged by any player’s flashy technique. Not that one shouldn’t play whole pieces; but I suggest playing sound-bytes first.

Here’s a checklist for what you can usefully listen for in a six-note chord. If you cannot hear each note [at least somewhat] distinctly, the solution is to keep on listening and learn how to focus your ear. In saying “focus” I mean just that: train your ear to focus on one quality of sound at a time — exactly as you focus on one person’s voice at at time at a well-attended cocktail party. Unless you’re playing a really bad guitar, I guarantee you: the information is all right there. The things to notice are whether or not, or how much, there is of any or all of the following.

1. A chord will emerge from the guitar either quickly or slowly;
2. notice whether any part of the sound dies off sooner, or lingers longer, than another. This is basic information that you won’t get if someone is playing whole songs;
3. listen for basic volume and presence;
4. a chord will emerge from the guitar either quickly or slowly;
5. listen for some degree of separation: that is, you may be able to hear each note. Or not: the sound may be fuzzy or cloudy and lack focus;
6. pay attention to the quality of sound — that is, whether it’s warm, sweet, tinny, rich, live, fundamental, shallow, breathy, open, held back, and/or has lots of overtones;
7. is there compliance of response? That is, do you have to push the guitar or does it respond easily to your touch;
8. listen to whether the sound is bass-heavy or treble heavy, or well balanced;
9. and whether the strength/presence of each string is even;
10. and whether there are any wolf tones (i.e., problematically louder or quieter notes)
11. and whether the guitar really plays in tune or not;
12. and whether the sound is good close-up, and/or from across the room (you’ll need a playing/listening partner for this);
13. and whether the guitar sounds different depending on whether you’re listening from in front of it or from off to the side. Some guitars will astonish you with how narrow their area of projection is;
14. and whether or not the guitar has good dynamic range; that is, whether can you get different quality of sound from playing very softly, softly, medium, harder, and/or really hard;
15. if you repeat these exercises with different chords up and down the neck you’ll get a sense of how evenly (or not) the guitar plays on the whole fingerboard;
16. be on the lookout for tonal bloom; that is, whether the sound comes out immediately at full volume or whether it integrates and gets louder before it begins to wane;
17. finally, you get to notice and decide whether and how much you like or dislike any of these qualities of tonal response in the guitar you’re playing.All the information is in the soundbox. You just need to know how to listen without having your ear get overwhelmed. And in addition to all these things, you can get a sense whether the guitar is easy or difficult to play; this has nothing to do with sound; it’s about how well the string action, scale length, string spacing, and shape of neck are adapted to your hand.

November 3, 2011

Q: Assuming you’re looking for a back to work in tandem with the top, as opposed to a reflective back, should the back also be thinned till it “relaxes”, as you do on your guitars?

A: Ummmmm… this is a really interesting topic that very few people have done any thinking about — and most of the ones that have are classic guitar makers, not steel string guitar makers.

The matter is too complicated for me to write fully about in this format, especially as I have written about exactly this kind of thing in my book. Have you read my book’s chapter on the functions of the guitar back? If you haven’t, it’ll be useful for you to do so. Mainly, my answer is based in the proposition that the job of the guitar top is to generate an optimal mix of monopole, cross dipole, and long dipole signal… which gets converted into sound a bit further on down the line. The back has a different function — although, frankly, almost no one that I know of has ever considered making a back that might have a purposely dominant monopole, cross dipole, long dipole, or whatever.\

The back has not been studied like that. And one indicator of this circumstance is that while guitar tops have been made with all kinds of variants of “X” bracing, double-X bracing, fan bracing, lattice bracing, ladder bracing, Kasha bracing, radial bracing, and even the most oddball experimental bracing, over the years… 99.99% of all guitar backs have been made with three of four parallel braces since the back was invented. Period. So our information about the possibilities of the back is limited to one model of bracing that has been done over and over and over and over again. I show some experimental back-bracing ideas on page 91 of my book The Responsive Guitar; take a look at them.

Also, consider that it doesn’t matter how the back is constructed if it is not allowed to be active. For instance, Bluegrass guitars are played with the guitar’s back resting against the player’s body. These backs are significantly damped out. That is, they are prevented from participating in the dances of the frequencies. Would it matter to that kind of guitar that the back has been thinned to the relaxation point? Not at all. That back isn’t expected to do anything. The technique of playing the typical bluegrass guitar (standing up, strap around shoulder, guitar resting against player’s body) does not concern itself with the back’s doing anything in particular except maybe acting as a reflecting surface and otherwise keeping the dust out. And, as I say in my book, (at the risk of becoming unpopular): the use of a highly resonant and expensive wood on the back of a guitar that has no use for a functioning back is to waste the wood.

But aside from all this, to get back to your question, the short answer is “yes”. My prejudice is to make the back more flexible than other makers typically do. The reason for making both the top and the back flexible to begin with is that everything else you do to them does nothing but stiffen them up. You brace them, dome and stress them, and attach the perimeters to the guitar rims. Pretty soon, you’ve got something that you’ve (perhaps inadvertently) made really too stiff.

But too stiff for whom? For you? Maybe; or maybe not. For me? No, I don’t really care. For the strings and their work? Yes: they care.

I first got onto this idea, years ago, from an interview with David Rubio in [long-since disappeared] Guitar And Lute Magazine. Rubio recommended thinning the free (unclamped and unbraced) top until it had no tap tone of its own. If it still had an identifiable tap tone, it would be introduced into the guitar’s structure and responsiveness. But if one introduces a “tone-neutral” top (or back) into the system one could then build an appropriate tap tone back into it by bracing it, attaching it to the guitar, and bridging and stringing it. The basic equation is: if you start out with this, and then add that and something else, you wind up with this + that + something else = something greater than what you might think you have..

November 3, 2011

Q: Do you use the same X amount of flexibility for all your guitar tops? Is there any reason to have a different, Z, level of flexibility when you use woods of different species? 

A: I certainly try to for the same level of stiffness in every guitar top I make, regardless of species of wood used, for reasons of consistency of sound and musical responsiveness.

However, it’s not quite a simple yes-no. The thing is, if you’re going to build a guitar that’s slightly bigger or smaller than the last one you made, then you’ll need to factor some accommodations into your measurements.

A bigger guitar top is weaker than a small one of the same absolute mechanical stiffness (i.e., the same mechanical stiffness is asked to cover a larger span or area), and will have to be left thicker to compensate for that weakening. And vice-versa. For example, imagine standing on a plank that serves as a bridge to cross a 5-foot wide creek, and a longer but otherwise identical plank spanning a 10-foot wide creek. The latter will sag more when you stand on it. Your weight is the same, just as the guitar’s string tensions are the same. The resistance over the span needs to be adjusted, however, if you want the sag to be the same amount.

That “sag”, in the guitar, goes to vibrating-plate motion, which has everything to do with sound. You probably don’t care how much sag there is in a simple footbridge, but in the guitar the ‘sag amount’ corresponds to how much or how little the guitar face can move and flex in order to produce sound. There’s a direct correlation, as sound is nothing but excited air molecules. Finally, we’re (you’re?) trying to build guitars that are optimally permeable and receptive to the strings’ energy level and budget. Assuming the use of standard strings of a standard scale — which goes to the energy budget — this implies the same (or at least comparable) optimal amount of structure.