About Intonation

Intonation....if you are a guitar player, you've probably heard that word many times. What exactly is intonation, and how does it affect the performance of the instruments.
Funny, I used to listen to the Beatles tracks on vinyl, and wondered why everything sounded like it was maybe not quite in tune, and then, in another passage of the song all was okay, and that resonate 'warbling' seemed to go away.
Well, what was wrong back then was their instruments, though they were some of the best for that time, were not properly intonated. In fact, Paul McCartney's bass guitar was almost impossible to intonate. It was a Hofner, and it was prior to Hofner's introduction of a truss rod. Being a short scaled instrument, as he played up scale (anything past the seventh fret) the guitar progressively became out of tune. I'll explain why in a bit, but suffice it to say there was not a lot the Beatles could do back then to make things better.
Since then, with the advent of digital remastering, they were able to take existing tracks and specifically correct the tuning of Paul's guitar, one note, and one song at a time. One of the big reasons digital remastering has caused some conflict with the original recordings.
Anyway, enough about that.
What is intonation? Basically it is re-defining the fretboard on any instrument to provide consistency in pitch as the guitar is played up scale.
A guitar neck is made up of a series of equations, and all have to coincide in order for it to work correctly. There is the scale of the neck, that is basically the distance from the inside of the nut, to the centre of each of the saddles on the bridge. Scale length can change depending on the instrument. For instance, a bass guitar can't be expected to have the same scale as a six string. And a dual octave, or twenty four fret guitar has a different scale length than a 22 fret instrument. Still, regardless of either, the centre of the guitar is alway the half way point. The Twelfth fret.
Other equations that fit into the mix here are the fretboard radius, the amount of relief on the neck, the thickness of the frets, and even down to the type and size of the string used on the instrument.
Basically, in a nutshell, intonation, depending on what other equations we have discussed, is the exact distance between the nut and the twelfth fret, and the twelfth fret and the bridge saddle.
Once a guitar is set up with the proper gauge of strings, and is tuned to whatever tuning it is normally tuned to (and believe me, there are many) the very last thing that is checked, set, or reset, is the intonation.
How is this done?
Most guitars, Fender, Gibson, PRS, G&L, Ernie Ball, and others, all feature a bridge made up of adjustable saddles. Intonation is set at the twelfth fret. The string is played 'open', and then checked at the twelfth. If the pitch of the note is higher at the twelfth than the open string, the saddle must be adjusted to compensate for all of the other variables we spoke of earlier. If the note rings higher than the open note, the saddle must be adjusted toward the tailpiece. If lower, towards the neck.
One would almost think the opposite, but keep in mind you are not tuning the guitar, you are selecting a bridge saddle position that best centres the string for both scales, on either side of the twelfth fret, which is the exact centre of the fretboard.
Years ago, saddles were not adjustable. One could fine-tune the bridge on the guitar, simple by moving it around. They floated on the guitar, and could be moved back or forth, and even tilted in order to get the guitar close to pitch.
Might have worked for the day, but that was really a poor approach to intonation.
A string's thickness also affects the intonation on the instrument, so intonation should always be checked when strings are changed to a heavier, or lighter gauge.
Changing the gauge of the strings also affects the relief on the neck. Relief also affects intonation.
Floyd Rose tremolos, are great for what they can do to change the sound of the instrument, but they are also a nightmare to set up, if you are not really familiar with them, and intonation on these can be a bit of a chore to set up.

What about acoustic guitars? Do they have to be intonated?
Of course they do. Acoustic intonation works much the same as their electric family members, the only thing different, is they usually feature 'fixed' intonation, by means of a compensated bridge / saddle. You might notice the bridge saddle slot on acoustics is milled out at a slight angle, never straight. This is the compensation for the intonation. Sometimes this is not enough to maintain the guitar's intonation and pitch, so the bridge saddle is further compensated on the bridge saddle. Have a close look if you own an acoustic, you might notice the saddle is stepped back, usually at the second string, to further compensate pitch.
A high end guitar might feature compensation on all of the individual strings.
It is important to remember which way the saddle goes into the slot when you remove and replace strings, because if it falls out and becomes reversed, your guitar is not going to sound right. Same applies for an electric archtop with a floating bridge. If the bridge comes loose as a result of string removal, you first want to maintain it's position as far as how it is facing the tailpiece, and exactly where it was situated on the guitar, to maintain intonation.
Always mark the position of the bridge on an archtop with a piece of black electrical tape. Simply align the tape with the position of the bridge prior to removing strings. Don't mark the guitar. After you reposition the bridge and install the strings, simply remove the tape. No mess, and no headaches.

Can you turn a right handed acoustic into a left handed acoustic guitar. Basically, no!
This simply will not work.
I have seen where the fella at the music store down the street, in order to make a sale, switched the nut on a right handed acoustic to a left handed nut. I would say he might have made up a new nut, but he wasn't that bright. He then went on to string the guitar upside down. This doesn't work.
Why?
Intonation! Plain and simple. The compensation on the saddle will be facing in the wrong direction, so as a person plays the guitar upscale, it continues to go out of tune.
Don't do this. It's not cool. If you need a lefty, buy a lefty. They make them everyday.
Regardless of the stringed instrument, intonation is a requirement.

Now, let's get back to Paul McCartney's bass.
Why was it sounding out of tune as he played the higher notes? He played a Hofner bass.
Back in the day Hofner never built a bass with a truss rod. Not even a steel re-enforced neck. So when Sir Paul used to tune his bass to A-440 hz, or piano pitch, the neck used to bow up on relief. This changed the respective position between the nut and the twelfth fret. The problem couldn't be rectified by adjusting the floating bridge on the Hofner 500/1, because the problem was between the nut and the twelfth fret, not the 12th fret and the bridge. So it would have been very difficult to eliminate in the day. Hofner has since corrected that problem, and installed a truss rod in their necks. Huge improvement.
Still, if Paul would have just used a Fender Precision back then, in all likelihood, that would never have happened. Thanks for digital mastering. The old recordings used to make me cringe.

So that is a bit about intonation. Maybe now you'll know what folks are talking about when they mention that word.
Till next time folks! Keep rockin'!!

Brett McNaueal