“Intonation is a social construct”. I’m not sure if I coined this phrase or inadvertently appropriated it, but I do say it often. All music is out of tune – it’s a mathematical impossibility for any three notes to be perfectly in tune with each other at the same time. That’s just science. We all have adapted to this mathematical anomaly and for the most part enjoy our imperfect music. Some instruments are more imperfect than others, and the guitar is one of those instruments that humans have struggled with since it’s invention. The frets need to be perfectly placed, and still the intonation is a compromise, with setup, string gauge, and the player’s technique all factoring in. If the frets are in the wrong place, it makes playing in tune all the more difficult. Gibson was placing the frets in the wrong place on their instruments for years, and nobody really noticed or cared. Recently I stumbled into this issue when I was refretting an older Gibson Les Paul for our friend Shane from the mighty Crowbar. Check it out.
Shane found a well loved, and much abused vintage Les Paul Custom (I don’t recall what era, but I believe it may be from the late 70’s or early 80’s). He immediately brought it in to us for an assessment, and I unfortunately had to be the harbinger of bad news: the guitar had been very poorly refretted in the past, and it would need to be redone. Refretting a guitar is something I do almost every day, so it should have been a straightforward job. Boy, was I wrong.
The previous tech absolutely destroyed the original fret slots, which were so wide that the fret tangs wouldn’t grab into the ebony. So to “fix” this problem they flooded the slots with epoxy, and just floated the frets in the goop. Needless to say, the frets were extremely uneven and just falling out of the neck. This job suddenly got a lot more complicated.
After removing the frets, I realized how wide the slots were, so I was going to have to add wood and then recut them all. I tracked down the most sturdy .5mm wood veneer we had in the shop, cut it up, and glued it into the fret slots.
Once I had the slots filled, I leveled the fretboard with our PLEK machine, to true the neck both for straightness and make the radius consistent. This process is accurate down to .1mm, so this gives us a perfect surface for pressing frets into. Having the fretboard properly prepped before fretting allows us to maintain as much of the new fret height as possible, minimizing the leveling required after fretting. Plus, it’s just fun to watch.
Then I programmed the PLEK to cut the new fret slots into the fretboard:
Here’s where things got really interesting. The PLEK revealed a ugly truth: Gibson’s frets were in the wrong place! When I cut the fret slots, the new cuts didn’t perfectly line up with the old fret slots. The cuts were slightly closer to the bridge in the lower regions of the neck, and closer to the nut in the upper regions of the neck, like so:
I was briefly perplexed, until I remembered a conversation I had with the engineers at PLEK when I was visiting them in Berlin. PLEK discovered that Gibson had been using an antiquated formula for fret placement, using a “Rule of 18” formula rather than the modern “12th root of 2” formula. I know, I know – you weren’t expecting a math lesson. But here’s the gist:
- The “Rule of 18″ is derived by successively dividing the scale length minus the distance from the nut to the previous fret by 18. Let’s say you have a Les Paul with a total scale length of 24.75″. Divide 24.75″ by 18 and you get 1.375″, which is the distance from the nut to the first fret. Now you subtract 1.375″ from 24.75″, resulting in 23.375”. Divide that again by 18 and you get 1.2986″, which is the distance from the first fret to the second fret. You then repeat the process for the remaining frets, dig? For the most part this works just fine, and people have enjoyed playing and listening to instruments with this fret formula for thousands of years.
- The “12th root of 2” is the more modern formula, which is based on how we calculate how notes are derived in standard 12 tone equal temperment. We use this to make all the notes as equally in tune with each other all through the chromatic scale. To determine fret placement, simply follow the same process as above, just substitute 17.817 for 18.
Now, what does this all mean for your guitar? In practice, well… nothing. As I said, intonation is a social construct, and we’ve acclimated to out of tune music, so don’t sweat it if your guitar isn’t perfectly in tune. You don’t need to refret your beloved vintage Les Paul to fix the fret placement, just enjoy it’s peculiarities and make it RAWK. What does this mean for Shane’s guitar? Read on.
It’s possible that Gibson may have screwed up the fret placement beyond the Rule of 18 difference (maybe this was slotted on a Friday afternoon), or the frets could have been so destroyed by the previous tech that some of them didn’t line up. But now that we have perfectly cut fret slots, we opted to make the most of it. I fretted it with Shane’s preferred fretwire, made a new bone nut, PLEKed the newly installed frets, and gave it a complete setup. Most of the old fret lines were covered up by the new frets, and only two at the top were exposed. I dyed them black and blended them in with the ebony board, and you’d never know they were there unless you looked super close with blindingly bright lights (which of course, we use in our shop). And even we can barely see them.
Intonation theory is a big nerd interest of mine, so I was eager to put this to the test. I played a lot of dense chords all over the neck, and it was very, very much in tune (or at least as in tune as mathematically possible). It certainly is more accurately intonated than many other vintage Les Pauls we have played.
Shane is stoked, and so am I. This guitar sounds massive, it plays beautifully, it’s super intonated, and it looks bad ass. I mean, look at this thing:
Now THAT’S what a well loved Les Paul should look like. Play the hell out of it, Shane! Enjoy!
P.S. How come I didn’t get the Crowbar bass gig when Todd Strange left? We literally have same last name! Give me a call next time, Kirk!