Sunday, July 11, 2010

Tune a 12 String Guitar

Many sites describe the basics of how to tune a 12 string guitar.

Hohner 12 String

After doing a bit of searching I couldn't find anyone that showed they knew how to tune a 12 out of the passion and pleasure of owning one!  So this article aims to take you beyond a boring, electronic tuner sounding, 12 stringed axe.

The harmonics and resonance qualities of a 12 string are remarkably different from a standard 6.  And there are some neat tricks to make your 12 string sound like a happy beast rather than a slightly detuned cardboard box!

To start with you need to get your guitar in basic tune.  An electric tuner will do the job albeit a little *too* perfectly.  What do I mean?  Well, hang on a minute, we'll get to that.  

Getting Started
The tension on the neck and body of a 12 string is huge.  You can't just tune a 12 like a 6.  It's more like tuning a piano: do it a few times to fine tune it and let the tension 'even out'.

Open the following page in new tab to get your at least your Bass E string in tune:

This page has an online tuner that plays the notes as they should sound.  This is a great place to get your 12 string into pretty good basic tune.  

Now, what's this business about my 12 string being *too* perfectly tuned?

Glad you asked.

A little background and way too much physics.
If this sounds too technical, skip down to Harmonics and Tuning Techniques.

When two strings are played at the same time your ear hears three basic notes: the fundamental note of both strings PLUS the difference in frequency between the two strings.  This third 'note' is called the beat frequency.

The beat frequency is what can make a 12 string sound awful OR beautifully chorused!

Let's say your guitar is in concert pitch, A440.  The frequency of the 9th string, the low A, resonates at 110 cycles per second or 110 Hertz.  (btw, A440 is 1st string, 5th fret.)

The thinner A string, string 10, is tuned one octave higher.  It resonates at 220Hz.

The 'first harmonic', by definition, is 2x the fundamental frequency, 220Hz.

If your two A strings are perfectly tuned, then your ear will hear 110Hz, 220Hz and a beat frequency of 0Hz.  Technically that means you hear no 'ugly' sounds.

In reality this will rarely be the case.  Playing on stage under lights, for example will change the tension of the strings and pretty quickly which affects the tuning.  But that's another issue.

Sympathetic Resonance
What happens if you pluck ONLY the 9th string?  The 10th starts to vibrate, doesn't it?  Good.  That's called Sympathetic Resonance.  

The 9th string is thicker and heavier than the 10th string and naturally stores more energy.  When you strum the strings, the 9th string vibrates at 110Hz and tends to "pull" the 10th string along with it (sympathetic resonance of the first harmonic at 220Hz).  

If the 10th string is *slightly* out of tune, the 9th string actually tries to force it into tune!  Nifty, huh!  However, this is also one reason why when you guitar is "in-tune" it may not sound right - there is a push-pull going on between the strings.

The main cause, however, of your 12 strings sounding like a week old squashed lemon is that the octave strings are out of tune by an amount that sounds a bit wobbly.

For example, let's assume the 9th string is at exactly 110Hz and the 10th string is 223Hz.  Your ear hears: 110, 220, 440 from the 9th,  223, 446 from the 10th and beat frequencies 3Hz and 6Hz.  

You don't really *hear* the beat frequency but you sure notice it.  The sound "wobbles" about 3 times a second, which the ear can perceive quite easily.  That isn't so much a problem here as hearing 220 and 223Hz or 440 and 446Hz.  Those combinations don't sound good.

Using an electric tuner the strings should be within 1Hz of the frequency they are supposed to be.  That's a good start.

Ever heard a Honky-Tonk piano?  Most of the keys around the middle of the piano actually have 3 strings - take a look inside!  To make it sound Honky-Tonk the middle string is slightly detuned.  It's *about* the right frequency but the slight difference changes the whole sound of the piano.  The same thing happens on your 12 string.

We have to find a way to tune the sweet-spot.  It isn't hard and here's how:

Harmonics are the best way to tune a 12 string.  (Harmonics on the guitar are made by just touching the string, directly over the fret, playing the string and then releasing your fretting fingers from the string.  The string will continue to sound a clear ring.)

It is vitally important your guitar has good intonation.  This means the harmonics are true to the frets.  A guitar technician can adjust this for you - on a good instrument anyway.  

Which Ones?
There are two sets of harmonics really useful for tuning and finding the sweet-spot.

The first, you may be familiar with from tuning a standard 6 string.

The 5th fret harmonic on the 11th string is the same as the 7th fret harmonic on the 9th string.

Using harmonics makes it easier for your ear to *hear* the beat, or difference, frequency.

To tune a 12 string beautifully, the main strings - strings 11, 9, 7 and 5 - must be tuned to each other just like a 6 string.  The octave strings - strings 12, 10, 8 and 6 - must then be tuned to the main strings.  Oh, and Rinse and Repeat!

Tip for the B Strings
The harmonic on the 7th fret, 11th string (Bass E) can be used to tune the 3rd and 4th (Open B) strings.  Depending on your 12, though, it may be better to use the normal 4th fret G string against the open B string.  You have to get a feel for your instrument.

Tuning Techniques
The sweet spot for a 12 string is found by "tuning-up" the octave string.  Tuning-up is important because it introduces some pre-tension to allow for the mechanical slack in the tuning peg mechanism.

How To Find The Sweet Spot..
Once the guitar is in reasonable tune, start with the bass E string pair:
  • detune the octave string
    • about half a turn of the tuning peg to start with
  • play the 12th fret harmonic on the thinner string
  • follow it quickly with the 5th fret harmonic on the main string
  • grab the tuning peg for the octave string and wind it up until the beat frequency disappears.  
  • If you go past the tune point, start again by detuning the octave string.
  • Tune the next main string just like a 6 string.
    • Do this for E to A, A to D and D to G.
    • I prefer harmonics but '5th fret to open' works too...
    • as does an electric tuner!
  • repeat this process until your guitar sings!
Tuning B and E
The B string is tuned from the 7th fret, bass E string, harmonic.  This is one octave and one fifth higher than the open E bass note.  Play it against the 12th fret harmonic of the B string, which is one octave higher than the open string.  

Next tune the third string to the fourth string, using the 12th fret harmonic.  The 5th fret harmonic is okay but is 2 octaves higher than the open string and you ear is less sensitive to tuning differences up there!

Next tune string 2 by playing the 5th fret on the B string against the open E 1st string.  i.e. you may find it difficult hear the harmonics here, so adapt!  Use the 'normal' tuning technique.

Again, tune the 1st string using both 12th fret harmonics between the 1st and 2nd string.

On my Hohner 12 string, pictured above, the E and B strings sound best when the E string is a "perfect match" and the B string has a perceptible difference - it sounds like a slight chorus effect.  

That's in tune, almost!  
Every instrument is slightly different and going slightly above or below the point your ear can no longer tell the difference between the harmonics IS the sweet spot.

Perfect tune?
A perfectly tuned 12 string sounds a bit flat.  That's what you get from a good guitar tuner.  A 12 string tuned to the sweet spot sounds brighter, has better sustain and sounds more pleasing to the ear.

As described earlier in the techie section, the difference frequency, the "beat" frequency, in a Sweet-Spot-Tuned-12 is small.  However, the ear, like the eye, appreciates variation.  

On the page you opened earlier the tuning sounds are perfect sine waves.  They sound flat, boring and very unmusical.  They are useful to help tune your guitar but you don't want your guitar to sound like that.

If you own a 12 string you owe it to yourself to learn to tune it by ear.

Incidentally, while I have never clamped my eyes on such a beast, I have been told the traditional design for a 12 string had the first two strings E and B at the same pitch, the G and D strings are one octave apart and the A and E strings TWO octaves apart.

If you have seen such a beast I'd love to hear about it.

Happy tuning and I hope you discover a quality in your 12 you never knew existed!

Other Useful Tuning References: (technical)

Restring Your 12 String - One Pair At A Time

Great stuff but can you hear his 12 is a long way from the sweet spot?

One more tip
If you don't need to be in concert pitch your 12 string may sound better detuned half or a whole step.  This reduces the overall tension on the body and means the strings are not as taught.  On many 12 strings this gives a fuller sound, longer sustain and can even add a warmth that you don't find in concert pitch.  Try it!  

Now you can tune your guitar beautifully you are free to mess about with some of those groovy alternative tunings.  And it won't drive you nuts everytime one of your mates comes over and tries to do you a favour and tune it up for you!

For the curious:
Paul is a recording sound engineer who trained at Metropolis Audio and the Audio Education Centre in South Melbourne, Australia.. way back when...  He also has a BA in Communication and Electronic Engineering from RMIT which means he had a seriously misspent uni life!

A bit of a hack guitar player, a better pianist and all round appreciator of creative genius, he seeks out people with passion and where interests collide, strives to help others bring out their best.

Comments and questions welcome.

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