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Old 05-23-2017, 02:18 PM
brianmay brianmay is offline
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Default What is an overtone?

In view of the thread complaining about rosewood's overtones, it became clear to me that I didn't have a clue what the OP was talking about despite playing guitar since 1964 (quite badly probably).

My two guitars are both Sitka Spruce tops and EIR back and sides.

Serious question: What is an overtone (in the guitar context)?
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Old 05-23-2017, 02:25 PM
Tico Tico is offline
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Overtone is the same in guitar context as in any other context.

Everything vibrates strongest (loudest) at its main resonance, aka fundamental frequency.
It also vibrates an octave above that.
Also, at a fifth above that octave.
Next, at a fourth above that ... (aka 2 octaves above the fundamental)
Next, at a major third above that ... and on and on in smaller intervals to infinity.
It's called the harmonic series.

As overtones go up in frequency they get lower in volume, and an untrained ear probably won't notice them but everyone's brain decodes their loudness ratio to identify what the source of the sound is.

Harmonic is another word for overtone.

Last edited by Tico; 05-23-2017 at 05:21 PM.
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Old 05-23-2017, 02:28 PM
jaymarsch jaymarsch is offline
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I'll give a stab at this from my limited understanding. I have two rosewood guitars that have a fair bit of overtones. When I pluck a string, it rings for a good period of time so when I pluck the next string, the first string is still ringing. This harmonizes with the sound of the second string and creates an overtone - a third tone if you will.

With guitars that favor the fundamental and do not create overtones tend to ring out when the string is plucked and then die more quickly so when the next string is plucked you hear the first tone and then the second tone with not much of an overtone created.

Does that make sense?

People have personal preferences and it also can favor different styles of playing and genres of music. Celtic airs can sound great with lots of overtones. Bluegrass and some fiddle tunes sound better when the notes can get out of the way of one another.

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Old 05-23-2017, 02:29 PM
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fazool fazool is offline
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I would be a little more specific.

Harmonic is the same as Octave. In vibration those are sometimes referred to as "orders", such as first order and second order - those are octaves.

Harmonics are usually octaves because they excite the easiest but "any" resonance can be a harmonic.

An overtone is when any other frequency becomes excited and elicited. Sometimes it is from aliasing, sometimes from straight orders.
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Old 05-23-2017, 02:34 PM
perttime perttime is offline
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There's a couple of articles on wikipedia that might help:

https://en.wikipedia.org/wiki/Guitar...nics#Overtones
"When a guitar string is plucked normally, the ear tends to hear the fundamental frequency most prominently, but the overall sound is also colored by the presence of various overtones (integer multiples of the fundamental frequency). The fundamental frequency and its overtones are perceived by the listener as a single note; however, different combinations of overtones give rise to noticeably different overall tones (see timbre)"

https://en.wikipedia.org/wiki/Timbre
"timbre is what makes a particular musical sound have a different sound from another, even when they have the same pitch and loudness. For instance, it is the difference in sound between a guitar and a piano playing the same note at the same volume. Both instruments can sound equally tuned in relation to each other as they play the same note, and while playing at the same amplitude level each instrument will still sound distinctively with its own unique tone color. "

Some guitars have very prominent fundamental notes - which might be perceived as "clearly defined" or "boring". Other guitars may have more prominent overtones - which might be called "rich" or "cluttered", depending on what kind of sound you want.
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Old 05-23-2017, 02:41 PM
Fattymagoo Fattymagoo is offline
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A great way to hear overtones in action is to look not at acoustic guitars, but at ride cymbals. There is a fundamental "ping" when a stick strikes the cymbal, followed by a "wash" of overtones that paint the overall sonic landscape of the cymbal. Different styles of music call for more or less fundamental tone vs overtone in a ride cymbal.

Going back to acoustic guitars, those ringing overtones can really fill space beautifully, but the can also get in the way if the music doesn't call for it. For me, I enjoy the sound of rosewood a *little better, but mahogany works a *little better with my vocals (the overtones fight my ears and pitch control... But just a *little)
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Old 05-23-2017, 02:41 PM
Tico Tico is offline
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A bit more ..
All vibrating things vibrate at their fundamental frequency, and every overtone in the harmonic series.

Interestingly, what makes a flute sound different from a trumpet playing the same note is the relative amplitude of the overtones.

This is the same reason your voice sounds different from your wife's voice when singing the same note, or just speaking.

It is like a code that our brains decodes.
Fascinating subject.

Last edited by Tico; 05-23-2017 at 04:45 PM.
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Old 05-23-2017, 02:44 PM
ataylor ataylor is offline
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Quote:
Originally Posted by Tico View Post
Overtone is the same in guitar context as in any other context.

Everything vibrates strongest (loudest) at its main resonance, aka fundamental frequency.
It also vibrates an octave above that.
Also, at a fifth above that octave.
Next, at a fourth above that.
Next, at a major third above that ... on and on to infinity.
It's called the natural harmonic series.

As overtones go up in frequency they get lower in volume, and an untrained ear probably won't notice them.

Harmonic is another word for overtone.
While I think I understood the general idea behind overtones, I don't know that I've ever seen it outlined this way. This explains exactly why some Martin D-28-style guitars I've played sounded very much like 12-string guitars.

Very cool!
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Old 05-23-2017, 02:48 PM
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Quote:
Originally Posted by brianmay View Post
In view of the thread complaining about rosewood's overtones, it became clear to me that I didn't have a clue what the OP was talking about despite playing guitar since 1964 (quite badly probably).

My two guitars are both Sitka Spruce tops and EIR back and sides.

Serious question: What is an overtone (in the guitar context)?
Hi BM
I'm with you when it comes to defining what people actually mean when they say things like that.

Certainly Rosewood sounds more lush to me than some other back/side woods, but I'm not sure it's overclocked overtone content people are hearing.

Sometimes it's sustain (useful sustain), or more clarity in trebles…especially with fresh strings, or deeper bass, or more projection, or tone which shifts when volume is added…and these may not even be related to overtone content at all.

When people refer to Rosewood having too much overtone content, I think I know what they mean (which is the important thing if there's to be conversation instead of ranting), and I kind of put it in the same category as saying Mahogany sounds 'dry'.

And come to think of it, I've heard people call lush tone 'wet' tone too. And Chocolaty, and warm, and silky, and lots of names which have little to do with the actual phenomenon under discussion.

At least 'too much overtone content' sounds more scientific than wet or warm or fluffy.

Whatever they hear and dislike about Rosewood, I think I like and appreciate and seek out for guitars I play. I suppose that's part of the reason guitar companies build guitars out of different wood combinations.



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Old 05-23-2017, 02:52 PM
Tico Tico is offline
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Quote:
Originally Posted by ataylor View Post
While I think I understood the general idea behind overtones, I don't know that I've ever seen it outlined this way. This explains exactly why some Martin D-28-style guitars I've played sounded very much like 12-string guitars.

Very cool!
I'm speaking from info recalled from a Physics of Music class at Uni years ago.
Some details may be spotty as I'm in my declining years, but the gist is sound.

Last edited by Tico; 05-23-2017 at 04:46 PM.
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Old 05-23-2017, 02:52 PM
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Erithon Erithon is offline
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Here's my attempt to break this down:

An overtone is a frequency higher than and mathematically related to the fundamental. The mathematical relationship is described in something called the Harmonic Series. All of the harmonic notes on a guitar (or any stringed instrument) are overtones derived from that fundamental.

The series occurs at the octave (12th fret), the fifth above that (7th or 19th fret), then octave again (5th or 24th fret), the major third (4th, 9th, 16th, and also somewhere beyond the end of the fingerboard), the fifth, the flat seventh, the octave... once an overtone is introduced it remains in the series as it goes higher and higher. So the further from the fundamental the more complex the overtones. Why these frets create overtones is part of the math. The octave doubles the fundamental frequency so it halves the string length; the octave harmonic does so by creating a "node" at that point which allows the string to vibrate at half the previous length. Over harmonics create nodes of 1/4, 1/3, etc. The ratio dictates the frequency of the overtone and thus which note is produced.

Overtones are naturally occurring frequencies. Back in the day, to make the distance between all notes "equal" so the circle of fifths and scales would work in any key, rather than be relative to the tonic, a slightly adjusted method of tuning was introduced. We still use this tuning today and, as a result, the more distance harmonics are slightly out of tune. For example, you'll notice that the octave harmonic sounds exactly at the 12th fret, but the major third harmonic is actually found just north of the 4th fret.

Overtones also dictate the timbre or "color" of any instrument. Only a pure sine wave is a frequency without any overtones. So the strength (or lack thereof) of each overtone is very different from instrument to instrument. This is why an A note on the guitar sound different from an A note on a piano ... and thus why a guitar sounds different from a piano. Each instrument emphasizes different overtones. This is also why orchestras tune to an oboe: its harmonic spectrum has a strong fundamental and overtones that reinforce that, rather than muddy it.

Even within individual instruments there is variation, and that is what the Rosewood thread you referred to is getting at. Different guitars will sound different to one another because they emphasize or demphasize different overtones and the fundamental. The body size, bracing, and wood all factor into this. So does where you play a note. An E on the 2nd fret of the D string sounds different from that same E on the 7th fret of the A string because the length of a string impacts which overtones are amplified.

Last edited by Erithon; 05-23-2017 at 03:17 PM.
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Old 05-23-2017, 03:02 PM
merlin666 merlin666 is offline
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Aside from the physical definitions on a more practical side the contribution of back and side materials have often been discussed, and in summary some claim they can hear a considerable difference between materials when all else is held constant and others suggest a minimal influence. One more substantial affect on the amount and composition of overtones comes from the age and the type of aging of the woods. A new guitar or guitar constructed from relatively fresh woods tends to have fewer overtones and more fundamentals, but as the wood ages and changes in cellular structure occur a higher contribution of overtones may occur to the vibrations. Some people call this "opening up" and view it as beneficial.
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Old 05-23-2017, 03:20 PM
Tico Tico is offline
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Read Wikipedia's article on Harmonic series.

I tried to link to it but the link didn't work.
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Old 05-23-2017, 03:24 PM
Inyo Inyo is offline
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Quote:
Originally Posted by Tico View Post
Overtone is the same in guitar context as in any other context.
That statement has an overtone of not ringing true.
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Old 05-23-2017, 03:27 PM
Tico Tico is offline
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Quote:
Originally Posted by Inyo View Post
That statement has an overtone of not ringing true.
Guitar is only one of many instruments.
Instruments are only one of many things that can make sound.

Overtones are basic physics of sound.
Bang two metal pipes together, or clap your hands together, stomp your boot on the floor.
Mic it and feed it into a spectrum analyzer, which displays frequency vs. amplitude.
It will show the fundamental and the overtones ... at precisely all the frequencies in the harmonic series.

The only sound with no overtones is a sine wave.

All this, of course, if your post was not just humor.

Last edited by Tico; 05-23-2017 at 03:36 PM.
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