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Having had no training and being the absolute novice that I am, can someone explain what I should be listening for in "Tap Tone" of a guitar top.
Is there a specific frequency that I should be aiming for? or is it just a personal choice of what sounds good to my ear?
Also a related question...What would you say are the maximum and minimum thickness dimensions for a Spruce top?
thanks...

Tap tuning a top is a personally developed skill, I say that because we each here something a little different when we do it. There are no set parameters, or tones to look for that will guarantee an optimally tuned top.
I personally use a combination of tap tuning, scalloping and parameter sanding to come to my final sound. That said, I am still seeking that signature sound. I suspect it will just develop out of building repetition and not out of something that I find in the process.

My basic plan is to thin the spruce top to around .120, there again, depending on its stiffness, I try to thin the top until I feel it break in, that is just as soon as it relaxes, but not floppy.
Then I add the braces. For the tap tuning process, I hold the top by the upper traverse brace and tap on the top side over each brace, top to bottom, as well as between the braces in the open areas.
What I am looking for is a tonal balance all the way around, from finger brace to finger brace.
To me it does not matter what the “note” is, as long as it stays constant around the parameter of the lower bout. Once this is done, I consider the top voiced. As far as I know how to voice a top.

Next the top is attached to the rim, box is closed and parameter sanded. At this point all im trying to do is free up the top. I feel for this by pressing the pad of my thumb down at the bridge location.
Again, this is purely subjective, and how I do it. Im feeling and looking for a flex here, when I feel the top loosen up. I’m done.

I hope this helps, and I hope I don’t get lambasted for my description, but it has worked for me.

To answer your last question, spruce top thickness. I generally end up at or around .110 to .120 for spruce and .135 for cedar. This is a pre braced thickness.

One note, most people tend to over build for fear of failure. I have tried very hard NOT overbuild and trust my instants. So far so good

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Lance@LuthiersForum.com

Like Lance said, we all have a feel for what we look for. I am much like Lance in my approach. I have to say that the most important thing for me is the the same as for Lance, a consistant tone in the lower bout brace perimiters. As far as determining a specific note to look for at this point in my skill level, I think would be foolish. Besides each top seems to have a differnt set of main tones and over tones.

Now I'm a complete novice too. I thought when you tap a top, you look for as may different "notes" as possible. This way, when you play the guitar, the sound is balanced. I would think that if you tuned a top to one consistent tone, then you would have a propnderence of that note in the overtones and might not get the whole harmonic series. Wouldn't you want to make it like a good gong where no one note stands out?

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Joe Breault
Merrimack, NH
Perpetual novice

Lance's comments are right on as far as I'm concerned.
I like to sand the bass side to a slightly lower tone than the treble, but I'm sure no expert!
If you have the opportunity to pick your top wood out yourself, there are a few things that even a rank novice can easily determine with a bit of flexing & tapping.
I beleive that a the perfect top should be stiff & lightweigt. When I'm choosing top for myself, I start by looking at the end grain & finding the best quartered pieces. Then I flex the top (gently) to get an idea of its stiffness. Then I check for presence of silk & make sure the runout is minimal by looking carefully at both sides together to see if there is a colour change evident between the two pieces. On a rough sawn top, you have to get the light just right to notice any change.
If the end grain is perfectly vertical at one end & angles off on the other, you know there is some degree of runout.
Once I find a few tops that look good, I gently grip the piece a couple of inches in from one corner with a thumb & forefinger. With the top held just firmly enough to not drop it, tap it in several places with a knucle. A "good" top should have a clear sustained ring. Keep moving your grip until you get the best response.
Personally, I like tops with a high clear ring, but others like a bassy sound. A really great top will ring for several seconds before fading out.
I don't have the experience to comment on tap testing backs & sides, but I understand that tapping can be useful when making a choice of which one to buy. Bob C. could probably offer some advice regarding hardwoods.
I hope this is helpful. AND.. the comments offered are to be considered my opinions only. I'm sure others will have different advice to offer.

Bill,
Thanks for asking this question.
It is great to hear what folks are doing, especially once you get the braces on. My assembly is a-la-Cumpiano so I assemble the sides onto the top first reather than the back first. I still have an oppertunaty to shave braces etc, before closing up the box. At this point in the assembly, I tend to agree with Joe's thinking. Would'nt you want the top and body to respond to as many different tones as possable?
"Gong" or "bell like" tone over the one tone?

Thanks guys, Great thred!

Wade

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Wade
Nashua, NH
http://www.wadefx.com

[QUOTE=JBreault] Now I'm a complete novice too. I thought when you tap a top, you look for as may different "notes" as possible. This way, when you play the guitar, the sound is balanced. I would think that if you tuned a top to one consistent tone, then you would have a propnderence of that note in the overtones and might not get the whole harmonic series. Wouldn't you want to make it like a good gong where no one note stands out?[/QUOTE]

I hope Allen jumps in on this one. It is right up his ally.

I like to hear a dominate tone clearly and consistant around the brace pattern. However the over tones are in there. Remember that when you attach it to the rim the top stiffens considerably. My feelings are that being a consistant tone around the brace pattern I have insured a diapharam that responds consistant about the bridge once attached. At this point if I feel I need to bring aout some bass I will thin the bass side scalops a bit. However I dont have enough acoustic knowage at this point to tune for a specific set of over tones. Instead, right now I tune for the tops best mechanical responce and this in-turn has provided a well balanced sound for me.

The responses have been great! thank you!!
In building the "Autumn" guitar I tap tuned the top both before and after bracing. I really just tuned it until it had more or less a "ring" to the tap rather than a "thud". I ended up on the thin side of the measurements mentioned above but but I think within an acceptable dimension.
I will keep all these suggesstions in mind while doing the next top.
Thanks!!!

Speaking of tap tuning.... (and not intending to hijack this thead...) Is anyone planning on going to Ervin Somogyi's class? I really wanted to go, but I have a conflict with the dates. It is a bummer he only does it once a year.

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Brock Poling
Columbus, Ohio
http://www.polingguitars.com

Bill,

For the science of 'Tuning' try to get Roger Siminoff's book, "A Luthiers Handbook". Also, Dana Bourgeois has written on the topic a fair bit (as well as a number of others). Siminoff talks about 'wolf' notes, where the air chamber as a unit is sympathetic to a certain note and amplifies that note when it is played, as Joe talked about above, so Siminoff suggests making sure that that note lives in a key that won't be frequently played. Anyways, I really like Lances description and will probably use that in conjunction with the stuff in Siminoff's guide.

Shane

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Canada

As you may know I am not a builder yet but find this subject of great interest. I hope that there are many more responses and I assume one may come from Alan Caruthers as this is down his alley. Ukuleles typically use fan bracing and some are starting to use a modified kasha bracing so I don’t know how the top tuning compares to an X braced guitar. Many of the ukulele tops are thinned out around the perimeter of the top plate to give more flexibility while still leaving the main part of the board stiff. They also use tap tones for tuning sound ports. The sound port is started and is opened up a bit at a time. When you measure a decrease in the volume from the sound port just add binding to bring it back to your last sounding.

Philip

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aka konacat

If you think my playing is bad you should hear me sing!
Practice breeds confidence and confidence breeds competence. Unfortunately, I'm stuck in practice.

[QUOTE=Brock Poling]
Speaking of tap tuning.... (and not intending to hijack this thead...) Is anyone planning on going to Ervin Somogyi's class? I really wanted to go, but I have a conflict with the dates. It is a bummer he only does it once a year.
[/QUOTE]

I wish. I was really intrigued by the pictures of Ervin's sugar cubes, so much so that I read up on his articles and website. I like the philosophy of building a guitar just strong enough. But the cost was a bit high coming from Australia. Let's see, trip to the US to attend a guitar building course, or a new swimming pool? My wife won that argument, the pool excavation is starting as I write.

Oh, and getting back on topic;
Bill, not sure exactly what you're asking, do you mean tap tone when voicing the guitar, or when selecting wood? The voicing parts been covered, so I'll add something from my own experience on wood selection for the newbie. When I was a novice (ok, so I'm probably still a novice) I did not have a clue what to listen for in tap tones. All the bits of wood I picked up seemed to go thunk, thunk when tapped. It was a bit of a revelation for me to realise that the important thing to listen for is what comes immeadiatley after the thunk. For a first guitar, look for top wood well quartered, little to no runout, that rings when you tap it. The frequency will change as you thin it.

Bill,

Tap tuning the top is as much a mystic art as it is a science I suspect but I find it an incredibly relaxing and theraputic thing to do. I tap along the length of all of the braces and listen for changes in the tone of the sound. I want to hear a "ringing" responsive sound everywhere and when I come to areas where the sound dulls or dies I do a little carving or sanding until it rings again. I don't do scalloped but "parabolicalish" profiling and it's amazing that tiny disruptions of the smooth shape can impact the tone a lot. The other thing I feel for (after reading something Dana Borgeois) is to tap the top on the bridgeplate area and let the tapping finger rest lightly on the top after tapping. You can feel the top "kick back" when you are in the ball park.

With the top attached and I thin down the lower bout around the sides and back part. Depending on top stiffness I have the centre part of the top at around 0.125" and these lower areas between 0.080" and 0.100". I also usually look for bearclaw tops as apart from loving the look (i's a love hate thing I know) I find that they tend to have greater lateral stiffnees.

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Dave White
De Faoite Stringed Instruments
". . . the one thing a machine just can't do is give you character and personalities and sometimes that comes with flaws, but it always comes with humanity" Monty Don talking about hand weaving, "Mastercrafts", Weaving, BBC March 2010

Hi Dave

I was hoping you would chip it on this one, I found the demonatration you gave me of your technique really facinating. After returning to my workshop I tried the bridge plate tapping technique, on my own instruments, and I am getting a clear recoil, I also tried it against an old instrument that I made, that I wasn't happy with the tone of and this one seems dead by comparison. When tapping along my braces I found over the scallops I get a more resonant ring (Not sure what this means yet). One I carved today I extended and shallowed the taper at the end of the braces, and the resulting tap tone seems far brighter, I will be interested to hear the end result.

Many Thanks for sharing your techniques.

Bill,
Are you talking about the "tap tone" of a top before it is sanded and joined or are you talking about "tuning" a top?

This is a much debated subject in Lutherie...When Torres was asked the secret of his success in building resonant classical guitar (which in general were louder and projected better than those that came before him), he replied by holding up his index finger and thumb pressed together and stated, "the mastery is between the thumb and forefinger" meaning that it is all a matter of subjectivity and skill developed over time.

Having said that I have read just about everything written about tap tones...such as tapping on various parts of the face to approximate the tap tone of 5ths, 3rds, octaves and such. In general I do as Lance has described but even using that type of method it always seemed that my sense of what sounded good changed over time and sometimes from day to day...it is TOO subjective...

So I had heard and read about Chaldni "glitter patterns" and the like but had never pursued it until hearing Alan Carruth speak on and demonstrate the subject in a workshop class at the ASIA symposium held in 2003 (held every other year for those not familiar). Alan not only has done alot of research into the subject but explains otherwise very complex engineering in simple easy to understand terms.

Once I had seen and heard his method of voicing a top I was sold. I use it before bracing a top, after it is braced and again once the body is together. When you are thinning the top the tap tone will drop as the wood gets thinner. When you brace the top the top will now be stiffer again so the pitch of the tap tone will go back up. Once you have attached the top to the sides the pitch will change further as the rim is now refining and restricting the tap tone.

I would highly recommend the articles on the subject on his website and in back issues of ASIA's Guitarmaker magazine (dont remember the issue numbers).

Since seeing Alan speak at ASIA 2003 I use his method religiously but will still listen to the tap tone and sounds I am getting out of the wood as the way that I see it using a method like Chaldni patterns only helps to confirm what you may or may not hear and will reassure you that you are hearing the right thing. The masters accomplished the same thing with their ears and fingers but that skill was developed over many years and to varying degrees by builder.

Alan is the one that I remember saying that the difference between a good guitar and a great guitar is in the details and having a way to verify what the tap tone is telling me has significantly improved the tone and volume of my guitars. I only build classicals but with classical guitars the voice (then the volume) of the instrument is everything. I am now getting a clearer, cleaner definition between each string with a first string that sings (in a classical that is a very good thing as the volume is much less than a steel string). I am able to get that without compromising or altering the "spanish sound" that I am building for.

I haven't read Siminoff's book, but some have described his tuning method
as impossible to use. Just a note of caution.Howard Klepper38678.145

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Howard Klepper
http://www.klepperguitars.com

When all else fails, clean the shop.

[QUOTE=Howard Klepper] I haven't read Siminoff's book, but some have described his tuning method
as impossible to use. Just a note of caution.[/QUOTE]

Ditto. This is the first time I've actually heard anyone agree with/give much credence to Siminoff's approach to the 'science' of tap tuning.

I heartily reccomend checking out the Dana Bourgeois articles (on his website), as well as perusing the various discussions in the archives here and the MIMF library. Quite a bit there, and quite some discussions of Al Carruth's signal generator methodology. His article on the subject (it's in the GAL Big Red Book volume 3) does help make sense of all the posts, though.

Russell,

Glad you found it interesting. The "dead" sounding one sounds an ideal candidate for some "ex-post top voicing" with a small fingerplane inside the guitar.

On tapping along your scalloped braces on the other guitar how did the sound change before/at/after the big peaks of the scallops?

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Dave White
De Faoite Stringed Instruments
". . . the one thing a machine just can't do is give you character and personalities and sometimes that comes with flaws, but it always comes with humanity" Monty Don talking about hand weaving, "Mastercrafts", Weaving, BBC March 2010

On th peaks it definately deadens, On the one I did yesterday I shallowed and legthen the taper from the peaks down. Taping along the braces it definatley seems more responsive.

Dave, Russell, it was the same with me. It was tapping the braced tops along the line of the braces and finding that the "duller" areas of the top seemed to correspond (on my tops anyway) brace points that persuaded me to go for a more parabolic shape to my braces. I build light and the pointy scallops seemed to have a very detrimental effect to me, I have been much happier with the attack and clarity especially on WRC tops since.

When I voice an unbraced top I hold it lightly by the neck join position and gently tap all over and listen for a clear note (any note) and equally thin the top until the note rings clear, wherever tapped, with a noticeable sustain. After bracing I do the brace tapping thing and sand them down until I have no dead spots and a lightly held top again has a good even ring to it. Once fitted to the sides I thin the top mainly on the lower bout bass side until the top rebounds at the bridge (this thinning pattern taken from Torres #FE19, he seemed to know what he was doing). Euro tops usually end up 100-105thou WRC 110-115thou.

I think the answer really is to find a way and stick to it and keep meticullous notes so you can remember what works. Over a number of guitars a system will develop that works for you and produce your "signature" sound.

Colin

Colin

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I don't believe in anything, I simply make use of a set of reasonable working hypotheses.

Bill,
   When i tune the top, I usually tap it as i make passes through the thickness snader initially and shoot for a point as close to its sustain potential as possible without getting it too thin to resonate. As more and more tops pass through your hands and machines, you just grow familiar with their inherent charachteristics and can read them a little more accurately before you even start so enjoy the learning process.

   After I brace a top, I will begin the tuning process by suspending it between my fingers holding at what would be the "nodes" or nonvibrational points along their length. These nodes usually fall around the point where the top transverse brace exits the edge of the top or where the top legs of the "X" braces exit the edge. As I suspend it next to my ear, I like to tap it in the area where the bridge will lay over the bridge plate and at several point along the line where the saddle will end up at. This gives me a reference as to the response I'm getting across the line from "E" string to "E" string.

    The process of relieving the bracsa by removing mass fom them is one that can be deceiving and can sometimes yield the opposite result that you were looking for depnding on the brace component that you're taking material off of. With a typical configuration including tone bars behind the brige are that are not placed symetrically on the top, the bracing system is one that doesn't inherently present symetrical disbursement of the vibration created by tapping or eventually by excitement by the strings being played. I pay close attention to the mass of each brace as i make my way around the top in a series of passes coaxing it to what appears to be it tonal and resonant potential, but I pay as much attention to the distribution of the overal weight of the bracing as a complete system across the top in all directions.

The finest violin builders of old always voiced their tops during the carve process and then finished them up after they were on the rim by cutting the recurve which is the thinnest portion of the top around its perimeter. The recurve is as critical a part of the overall voicing process as the carving and shaping of the top and the distribution of the mass and weight on the top surface. As the instruments built by the finest violin makers have been restored by being disassembled over the years it is a common discovery that the graduations in the top thickness are not symetrical, but vary from one point in a half of the top or back to the corresponding point on the other half. This clearly indicates that the distribution of the mass is an important factor in the final tone results. We need to pay attention to that aspect of building as well as weigh reduction overall as we scoop material off of our braces.

After the top is on a guitar body, we can recreate the effect of the recurve of a fine violin by thinning the top around its perimeter and freeing the vibration of the top in the critical center area surrounding the bridge without compromising its strength and integrity and jeopardising the longevity of its service life. Any builder will tell you that there is another phenomenon that occurs during the build as we add the binding package to the mix. When the body is unbound, there is a distinct and powerful tap tone present, but when binding is added, the joints where the top, back and sides become a unit are solidified and create a more integral unit as the components work more efficiently as a system.

   The tap tuning process both before and after the plates are on the body is a fun and interesting one to develop and learn as you build. With time and numbers of guitars, you just develop your own methods and techniques for coaxing the most out of each piece of wood.

Have fun,
Kevin Gallagher/Omega Guitars

I used to read all the articles on 'tap tuning', and never could make head or tail of them. What does it mean, for example, to 'thin until the fundamental goes away'? The fundamental is just the lowest tone in the series: there's always going to be a lowest tone!

I got to 'track' Dana Bourgeois through part of his voicing process at a GAL convention once, and now I 'get' it a little better. He had the guitar assembled, and I was able to check the 'glitter patterns' and the main air mode frequency. Then he started to thin the edges of the top until he got the 'kick' he wanted. Then I checked it again. It turned out that what he was doing was tuning the pitchs of some of the top resonances to match in well with other air and body resonances: for example, thinning the top out dropped the pitch of the 'main top' resonance until it could couple effectively with the 'main back' mode. When you get this and tap on the bridge the top pushes the air in the body, which pushes the back, which in turn moves the air and that shoves back at the top. There's a little delay built in between the time you push in on the top and the time that the back pushes back on it, and that's the 'kick'. He's getting this with several different modes when it's all working well.

The results are that the guitar is more effective at producing sound, and also the sound is more complex. Both of these are generally good things.

The 'glitter pattern' method is pretty much just a way of making the resonant patterns that you hear and feel when you're doing 'tap tuning' visible, and assigning them exact frequencies. It seems to me, from what I've been finding out in the past several years, that the _shapes_ of the patterns are far more important than the frequencies. You can get all of this information without the high tech gear, but it's harder in some ways.For example, I was interested that some of you try to get 'the same' pitch all around the edge at the brace ends when you tap. This would be characteristic of a 'closed' ring for one mode in the lower bout, and I've found that to be a good quality indicator.

I'm happy to hear that Shawn has had good results with this. Most of the folks who have tried it for a while seem to like it. It does seem to take a lot of the guesswork out, and I like the idea that I can build a pretty fancy guitar and know that it's not going to sound awful when I get it done. There's nothing so dissappointing as picking up a beautiful instrument that sounds dead!