Staying in tune is one of the most basic expectations we have for a guitar. It can be incredibly frustrating when a guitar can’t even get that right.
There are two main reasons a guitar goes out of tune: Friction and temperature. Either the string is slipping (not enough friction), binding (too much friction), or the temperature is causing the strings to expand or contract.
Whether it’s a single string that keeps going flat, or you have to retune all six strings every few minutes, a little bit of guitar physics goes a long way. No, this won’t require a lot of science. Just a few simple ideas to help you troubleshoot your tuning problems.
There are solutions for pretty much any tuning problem. And they don’t involve chucking your guitar into the nearest body of water.
Friction
The most likely culprit if your guitar won’t stay in tune is friction. Friction is resistance—or opposing force—when two moving surfaces make contact.
In the case of a guitar, friction occurs wherever the string makes contact with part of the guitar. Guitar strings have three primary points of contact:
- Bridge Saddles
- The Nut
- Tuning Posts
Fender-style guitars also have string trees that place additional tension on certain strings behind the nut. These can get rough or worn out if they’re not cleaned and polished from time to time.
Some guitars—like those with Bigsby or Fender offset-style vibrato systems—can have additional (unintentional) contact points. If you have one of these instruments, it’s important to look for every place where the string touches something.
The most obvious sign of binding strings is a high-pitched “plink” sound when you tune the guitar.
Saddles
Every time you pick or pluck a note, bend a string, or add vibrato to a note, you are tugging on the string. This pulls both ends of the string inward, allowing a small length of string to slide across the nut and saddle.
Saddles with pre-cut grooves must be filed for the correct string gauges. If your guitar came with 9’s and you switched to 10’s, the groove could be a little too small. Unless you are comfortable with widening the slots yourself, get a professional tech to ensure your strings fit properly.
Fender-style guitars with barrel or block saddles can usually accommodate various standard string gauges.
Regardless of the style, saddles should be smooth and polished where the strings sit. Burrs and rough spots can increase friction and cause strings to snag. They can even wear away at the strings and cause premature breakage.
As long as the saddles are in reasonably good condition, a little 400-grit sandpaper should be enough to smooth out any rough spots.
The Nut
All of the string slots in the nut must be cut to accommodate your string gauges. Even if you are using the same gauges that came with your guitar, they may not have been perfect to begin with.
The nut is usually the source of that “plink” sound you might be used to hearing. If you’ve increased your string gauges, you will need to widen the slots with a set of proper nut slotting files or hire someone who can do it for you.
Slots that are a little rough or bit too snug can be smoothed out with some 400-grit sandpaper.
You can also lubricate the slots with a bit of graphite pencil lead or petroleum-based lip balm products. I prefer to keep the slots clean and smooth because these other options can be messy.
Tuning Posts
The tuners are one of the first places guitarists look when they experience tuning problems. After all, those are the part that control the tuning.
Even cheap tuning keys are well-made enough to avoid slipping gears. Tuning keys tend to have a couple of problems. The first is the string winds can slip up and down along the post. This can lead to slight variations in pitch.
The most frustrating tuner-related issue is the strings slipping out of the post. You may notice this problem when you tune up a string, but it won’t tune high enough. Or you get the string up to pitch only to have it drop significantly moments later.
This can be the result of poorly machined tuning keys, or imperceptible wear that allows the strings to move more than they should. Sometimes polishing the posts and string holes can be enough to fix the problem.
Some players wrap their strings around the posts in an overlapping fashion that locks the string in place. I prefer to eliminate this variable by installing locking tuners on all my guitars. Locking tuners also make string changes take less time.
Temperature
Another cause of tuning instability is heat and cold. Like most natural materials, the metal in guitar strings expands when heated and contracts when it gets cold.
Typically if you leave your guitar on a stand when it’s cold, the tuning will be sharp the next time you play it. That’s because the strings contracted, making the wire shorter and pulling them a little tighter.
During the warmer months, the metal will expand. That makes the strings a little longer and causes the tuning to go flat.
While there is no way to prevent this natural phenomenon, you can prepare for it.
Whenever possible, let your guitar acclimate to the setting where you will be playing. Hot stage lights can make a guitar go flat in a hurry if the strings aren’t warmed up. Do the same when playing outside in the cold.
Old Strings
This should almost go without saying. Whether your strings are cheap or old, a bad set of strings won’t hold tune like a fresh set of a trusted brand.
If you’ve already eliminated string snagging at the saddles and nut, and slipping at the tuning posts, the strings might turn out to be the culprit. Even a brand new set can have imperfections that affect tuning stability.
Strings with inconsistent diameter, rough spots, flat spots, dents, or dirt can get snagged on the nut or saddle slots even if they are properly cut. If your strings look discolored or damaged, install a fresh set and see if that clears things up.
Bad Instrument
It’s pretty rare these days to get a “bad” guitar from any of the big brands. Most of the time, tuning issues you might find on a professional-grade instrument are caused by the causes described above.
That said, a cheap or poorly-made guitar can have problems that make it virtually unplayable. The bolt-on neck shifts around in its pocket. The truss rod won’t hold the neck straight. The strings snag on screws, fret ends, and any other surface you might never consider.
A professional guitar tech can evaluate these kinds of issues and determine if they are fixable and whether they are worth the trouble to fix.
Conclusion
The guitar is a fairly simple machine. If you know the causes of tuning problems, it’s not that hard to troubleshoot. It is rare that a “bad guitar” is the best explanation. Most bad guitars can be fixed, assuming they were ever “bad” to begin with.
Even expensive high-end guitars are subject to the laws of physics. All it takes is a little bit of thinking to determine where the strings make contact and whether the issue can be explained by something as simple as the weather.
Mike Eiman 