Tap tuning

[Dominic]

Bob, I saw you comment on tap tuning on the OLF.

"I only listen for sustain over the lower bout of the soundboard.

And usually I'll hear a bottom end rumble as well as some high frequency component
in the tap tone but it's the decay that interests me - not specific frequencies.

Cheers

Bob"

I'd be very interested to here how you go about it and what it is exactly you are listening for. Also anyone else who has some thoughts on this topic.
Cheers
Dom

[Allen]

I've never seen anyone else tap tune a top, so I just go by the seat of my pants and just give it a good plonk on the top directly over the bridge plate. I hold the top at about the 10-11 o-clock position.

As I start shaping the braces I stop every now and then and give it a few more taps. All I'm doing is getting an idea of where the top was and where it's going tone wise.

Once I'm getting reasonably close to what I think the braces should be, I give the top a good tap with my finger all around the lower bout. Like Bob, I don't listen for any particular tone. Just if it rings or not, and the sustain. I keep shaping until it's ringing nicely.

I've no idea at all if I'm doing it correctly, but they sound pretty good when they go together, and you can feel them tremble under your fingers once they're strung up just by the sound of a persons voice when they are near by.

I would truly love to be able to learn more about this. Hands on with someone who really knows what they are doing would be ideal.

[Taffy Evans]

Hi
Dom and Allen I just spent hour and half writing up my experiences with tuning plates, I just looked up from the key board and it has all disapeared. Any idea why this might happen. Not happy.

[Bob Connor]

You seem to be doing basically what I do Allen.

I guess the first thing I want to know is who am I building this instrument for and how do they play or what do they want the instrument to do for them.

Someone who wants to flail the living bejaysus out of an instrument certainly doesn't want Engelmann or Cedar so Sitka or Red or Lutz or Euro left a bit thicker would be the ticket. For someone with a light touch I guess you could use anything and thickness it down to what would be suitable and then brace and voice accordingly

If the strings are attached to the bridge and I want the strings to sustain, it stands to reason that I want the free plate to sustain when I tap it around the bridge plate.

So most of the tapping in the early stages is done around the bridge area and holding the top on a node. The node that I like is in between the X-brace and finger brace on the treble side. And I 'm listening for sustain in the upper mids, maybe around 1KHz- 2Khz

Dave will hold the top somewhere in the upper bout and I think he listens for sustain at around 100 Hz.

Once I get it sustaining reasonably well, I'll tap all over the lower bout paying particular attention to where braces meet. If they're a bit dead in those areas I'll carve a bit more off.

Most of what Dave and I do is variations on the Martin X brace so it's pretty hard to make a total bollix of something that's so tried and tested.

If you have some understanding of how the monopole, cross dipole and long dipole modes work you can make subtle variations in your bracing to try and change the characteristics of your instrument.

I'm pretty sure most of us are building the buggers and crossing the fingers when the strings go on because you just can't ever be sure of what you are going to get.

I'd recommend John Mayes' videos particularly the Advanced Voicing one and there are some Ervin Somogyi videos here (that I'm not supposed to have) that are pretty good at explaining the dipole stuff.

[Taffy Evans]

Hi There
I've played with the tuning of plates and air chambers for over 30 years, so you would think I would know what I am doing...not! I'll bet i'm not far ahead of you guy's. Doing it is one thing putting it all together and making it work is another. Before I discribe the methods I've used and the hours I have waisted trying to crack it, I'll share my understanding. Over all those years I have never had anyone to discuss it with either, and reading is not my prefered learning style, hence the waisted hours. I understand that there are desirable notes for the back, top and the air chamber that contribute to the tone, timbre and volume of the instrument. I understand that these notes should work in a way that will enhance the notes played on the instrument. We have all played guitars where a 'd'or a 'g' chord sound so full and rich and stand out over the others, well you could find the the resonant frequecy of the sum total of the parts mentioned above are a 'G'or a 'D' or close to it.
Tap tuning gives me a starting point and what I hear is mainly the quality of the tapped tone and as mentioned the duration. This has indicated to me the type of bracing that might be needed to get 'that tone' thats in my head, different grain counts and hights and so on. In the early days I was trying to get notes that did not fight each other, like stereo speakers out of phase, or beats like a two strings out of tune. I persisted with this for years. I was being told that my guitars were very loud, this was more noticable in smaller bodies as one expected them to be quieter. This is not an endorsment, but during this time. in "Alice Springs" I asked Tommy Emanuel two try two of my guitars, a smaller dread and an OM size, his main comment other than them being too cheep, was they were loud like big Gibsons. This was pleasing to hear but was it due to my attempts at tuning????

As I said I started tap tuning hanging the plate as described by Allen and recording the note. As braces were added I continued tracking that note through the gluing and shaving of braces. I would hum the note I heard into my guitar tuner and record it on paper. In the late 1970's early 80's I met Ian Noyce a fine builder in Victoria and bought his old Conn Strobe tuner, a valve job. This was my set up [I 've got photo's somewhere], you would be aware of this process.
I had a 12 inch speaker in a box this was connected to a signal/tone generator. The plate being tested was positioned over the speaker so that as I swept the generator through a range of tones it hit the plate. What I was looking for was the fundamental frequency/note, of that top or back. Carleen Hutchins wrote a lot about using this method on her violins. When the note of the plate matches the generated note the plate comes alive and gets excited. I could see this change by have brass filings on the plate that suddenly change the way they moved on the plate. I could also find the areas of no vibration, nodal points. I then placed a microphone above the plate that went into and amplifier and then into one side of a duell trace Osciliscope, two screens. The tone generator when through one screen and gave me a wave form the note of which I could read on the tone geny. The mic picked up the same signal and fed it to the other screen, it showed the same wave form only with less amplitude. When this wave form jumped high I figgered the plate under the mic was exited, and I was seeing the fundamental frequency of that plate. I noted it down and so on. Believe it or not I also had a large stobe light that when hooked up through system could freeze the plate at any frequency so one could see the different modes and areas of vibration. All sounds good and very impressive, but you gotta know how to use the info you collect. I think I do to some small extent. I dont have that gear now. But I still tune plates and stumble along. So long as I get even volume across all strings up and down the neck, a tone that me and the customer are happy with, and good volume I'm happy.

I don't know if this is a result of all things comming together correctly, but when I pick single strings I want to hear other strings that are sympathetic to the note played become exited also, and ring along even though they are not plucked. this is what may give me the volume in my guitars. Mind you having not talked or mixed with other makers I could be writing complete crap. No questions please just solutions, only joking. Thanks for reading, I'll value your comments.

[Hesh1956]

What I do sounds a lot like what Bob does.

My process starts with only the X-brace glued onto the top. With only the X-brace I tap all along the X-brace's path and carve it as a result of what I hear.

Step one for any brace for me is to use finger planes to carve the brace into a triangular profile. Once this is done with the X-brace I tap along it's path and note where it is dead or "thuddy...." sounding. When I encounter a dead spot, and the intersection is often one of these, I look and see if there is an opportunity to remove more mass from the sides of the braces first again making a triangular priofile. At the X-intersection since the planes won't get very close to the intersection it's chisel time. If the intersection has not opened up and rings I check the height. I know from building other guitars that for example I am safe to take the X intersection down to 1/2" in height for an OM or smaller guitar with light gage strings.

So to be more clear - if it thuds I remove more brace material from the sides of the braces and if that is not an opportunity I remove material from the top of the brace if it is safe to do so depending on the brace and location.

Now after the top rings every where with only the X in place I add other braces, a few at a time, and repeat the same process. My goal is to be able to tap the top at any location and have it ring loud and clear. This includes the entire upper bout too although this area will surely be muted by the fret board. Like Bob to me progress with the ring also means greater sustain too.

This is all done by ear and feel, which is what I wanted to learn from the get go.

Where you hold you top too is very important. I hold mine along one side as close as I can get to 25% of the height of the top from the top. This is a node and the top will ring very well if held here.

Also like Bob the intersections of braces are often problematic and I will pare/feather the intersecting brace end down in these locations until it rings and has a certain flexibility in my hands that I can't describe in writing - it's a feel thing.....

Again the process is repeated, adding a few braces, taping, listening, removing mass from the sides if possible, and the reducing the height if I need more mass removal and it is safe to do so. And always my braces are carved into a triangular profile first before the tapping begins.

I find that when the top has all the braces in place and it rings very well and I add the bridge plate it often rings better and stronger and no further action is required.

Also, for smaller guitars and since I use parabolic/tapered braces I often want to increase the bass response. I find that reducing the height very slightly of the bass leg of the X on the lower bout seems to enhance bass. It also gives that half of the top a lower note when I tap it. The resulting guitars that I have done this too have better bass IMHO than my previous guitars.

If I didn't make this clear prior I am taping every where on the top, following brace paths, taping the edges, every where.

I noticed Bob's comment on the OLF too and think that it is an important statement for folks who need something to start with as they learn to tap tune.

I'll add that it is something that HAS to be experienced and one learns very quickly just by doing. Making some test tops solely for the purpose of learning is highly recommended and very rewarding. Tap, listen, improve, listen again, and repeat and in short order you will hear the differences. Feel your tops, flex them in your hands often, press your thumbs in the bridge plate area and feel the level of stiffness of lack of same. It's all good stuff and you will develop a feel for this art.

Lastly how do you know when you have removed to much brace mass? When the volume of the resulting ring starts to decrease. I have only experienced this on a test top and never on a top destined for a guitar and I am grateful for that......

[Bob Connor]

I agree Hesh that you just need to do it and get a feel for it and I really don't think that you have to over-complicate this tap tuning stuff.

I think it's really difficult to build a bad sounding guitar, in fact with some guidance and advice most builders first and second, maybe third instruments can sound every bit as good or better as some of the high priced factory instruments.

The difficult part is how to transition from a good sounding guitar to a great sounding guitar. And that ain't going to happen overnight. You just have to keep building and researching and keeping notes and developing a feel for the wood and tweaking and asking questions and .....

[snidermike]

I do things similarly to Bob and Hesh. I don't start tapping until all the braces are on, including bridge plate. I don't listen for a particular note. I've also had the luxury of working with and being a student of Robbie O'Brien's, where I can go around flexing, tapping, and listening to dozens of students' tops, which really helps to get a feel for it.

I definitely like to be flexing the top a lot as I go too, before gluing it to the rims. I've just started gluing the top on before the back too. I'm trying to get a feel for how that should sound once it's on without the back on.

[Jim Howell]

I've pretty much done it as Mike Snider has described. I don't listen for anything specific, just a good ring and some sustain. I also think that Hesh is onto something and I'm going to adjust my method to start tapping as soon as the X-brace is on. I've always glued up all the bracing pretty much in one fell swoop in the go-bar deck, but now I can see some real benefit in slowing down a bit here. When one speaks of taking that big step from making a good sounding guitar to consistently making a great sounding guitar, I suspect that this is the major area to figure out. Tapping sure seems to help as does keeping accurate measurements and notes.

[Dominic]

Hey everyone, thanks for the thoughtful comments. And Taffy, thanks for doing it twice. Sorry to not get back sooner, been too busy. I'll have some things to say tomorrow.
Cheers
Dom

[Dave White]

Hesh,

It's interesting that you put the bridge plate on last - I have that on immediately after the X braces as that's where the top's "agitation" will start from and I want to hear how it responds with it on as each brace is added and carved. Interestingly, the most important brace in my experience to go on after the bridgeplate in terms of maximum impact on the top's responsive properties is the upper transverse brace. The top comes totally "alive" with the addition of this brace. But as you know, I believe the upper bout to be an important habitat of the "tone fairies"

[Hesh1956]

Dave mon I notice that when I glue on the UTB and carve it the top comes alive in the upper bout too.

Like you I am a fan of making the entire top ring not wishing to leave anything that might be there behind.

Irregardless of the order of the additive process of bracing I think that we both notice that when the braces are in place, and carved, the tops become more alive.

I once heard a top described as being a spring - full of potential energy. If you forget about the connotation that the top may be under tension which I don't think that the spring analogy was meant to say I like this spring idea.

[Robbie O'Brien]

Tap tuning...hum, where do I begin?
This subject I address thoroughly in my guitar building classes. Like Mike said, it is very advantageous to have another 15 or 20 tops to tap throughout a semester. It takes some guys years to be able to have this type of experience. It is fairly easy to understand when you are able to have a hands on live demonstration. Trying to explain it in words over the internet is much more difficult than it sounds. I think everyone here has done a good job of explaining. I am in the camp of listening for sustain and resonance rather than a specific pitch. I explain it to my students like this. You start with a perfectly good piece of wood and join it. It has a decent, ringing tap tone. You then thin it until it sounds terrible. The nice ping has gone away. You then put a bunch of braces on it and it now sounds like a 2 X 4. You then start shaving braces until that ping and resonance starts coming back. The more you shave the better it gets until you get to a point where you notice no more improvement. You also have to worry about structural integrity throughout this process, especially on a steel string. I want the final tap tone to sound like a gong. I want a strong fundametal that resonantes and has a secondary life to it.
I know this is hard to absorb without seeing it done. The good news is that I am currently working on a DVD with Kent Everett on this topic of voicing an acoustic guitar. It will be actual motion video with tap tones etc you can hear as he voices the guitar. We have finished the filming stage and are into the editing stage. I hope to have it out in a few months. I will keep everyone posted.

[Dominic]

This discussion is looking interesting. I play a lot and have a very fussy ear. The more guitars I get/make the harder it is to settle on one. I suppose continuous ageing of the guitars, changes in humidity and maybe changes in what my ear is hearing and the songs I play mean I want to keep switching guitars. I am looking for particular sounds.

I read the Roger Siminoff book a while ago and for want of a better reference point I use his technique. This means for me that I tune (if that is what I am really doing) the top after it is attached to the sides. This seem to make sense to me as the top will sound a lot different when attached all around its outer edge than when held from a corner. I am not at all concerned with the aesthetics of gluing the back on last as I am going for a sound quality in my making. But its not that hard to clean up any glue anyway.

Then, according to RS, I aim to lower the note that the top plate rings at by shaving braces and thinning the edge of the top plate. I record the note.
Unlike Taffy’s amazing sounding setup I just use my guitar tuner and humming to get a rough idea.
(BTW, Taffy sounds like the kind of guy we could use on our Maralinga project.)

And like others mentioned, I try to free up dead spots and get the top ringing the same all over.

But beyond that, one of my guitars is a small OM style. It is really loud but with fast tempo finger style the notes blur. It is like it sustains too long. I kind like it but then I can also find it too harsh sometimes and not very sweet.

What kind of sounds do people go for in their guitars and how do you go about getting it?
Cheers
Dom

[ozziebluesman]

Interesting discussions going on here alright!

This aspect of guitar building is so intriuging. The John Mayes Advanced Voicing DVD touches on this subject but it is limited. I have no experience with tap tone but with my last two builds I have tapped the tops consistantly on both guitars during the build listening for differences and taking notes.

Here are some observations i'd like to share:

One guitar is sassafrass and the other blackwood. The sass guitar is much lighter in weight compared to the blackwood yet the pitch of the sassafrass is D and the blackwood is a semitone higher in pitch at Eb. The sassafrass guitar has 10mm x 10mm braces except the transverse brace and the blackwood has 9mm x 9mm braces except for the transverse brace. Both bracing have the same scholloped feathering of the brace ends and just lightly sanded. Braces are tucked. The Blackwood guitar is 5 mm thicker all round to the sassfrass guitar. The blackwood being denser has a longer sustain.

When thinking about the tonal possibilities for these two guitars before starting the build I decided to make the blackwood guitar deeper and brace is lighter due to woods heavy weight. I expected the end result would be a deeper pitched instrument. Not the case! The only thing I can think of is the X brace may be a little wider spread on the sass guitar and hense, a deeper pitch.

Basically while voicing both tops I tried to get an even tap tone across the entire bridge area of the top. Again, I'm a beginner and trying to learn.

Again the blackwood may open up in time but I don't think the pitch will change.

If anyone has some thoughts here, greatly received.

Cheers

Alan

[Taffy Evans]

G/day
Hey Dom to be honest I did not have to do my post twice, I just kept clicking on things to close down in frustration and it suddenly reapeared.
About the Maralinga comment, yes I could work on that project if you wanted a shed built. I was given most of this gear, and more, by a guy who work at the over the horizon tracking station in the NT. He must have thought I had too much time on my hands.

However on my last 10 or so guitars I have used actual tapping and stroking of the timbers to test and compare responces, I enjoy this more, and I feel I'm getting good results. I think I only played with all that gear for a year or so. As I've mentioned I've worked in a vacumm all these years and for me to understand something better I find it easier to try it. Then I suppose I can say "well it did'nt work for me".
Like you, I thought that why do I do all this tuning and glue the top to the sides and wondered if the whole deal changes and how. I have a form that represents the sides and to which I can temporarily fit the top or back, I tap and tune in the form. I also use my guitar tuner, and a strobe tuner. I have only done one guitar this wayand only because I wanted to better understand what I have read. And if this guitar compares well to others I built recently, I say "well this did work for me". I would think we all have a slightly different take on tone and how to get it. Reading all of the above it could appear we are doing pretty much the same, give or take, to what others are doing. However maybe the final reward for our efforts is the smile on the customers face, after those first few chords.
Very informative thread thanks guy's.