Why your guitar won't stay in tune

You tune the guitar, play for ten minutes, and it is already sour. Why does a guitar keep going out of tune? Almost never because it is a bad guitar. A short list of ordinary causes covers nearly every case, and they are not equally likely: new strings, the way you tune, the room and the nut account for most of it, while worn tuning machines and a moving neck come much further down. This page goes through them in that order, with the symptom that gives each one away, and a five minute test with the tuner below to tell them apart.

Start with when it goes out of tune

Before you touch a screw, notice the moment the tuning moves. That single observation narrows the list more than anything else.

• Right after a bend or the whammy bar: look at the nut, the winding at the tuning post, or the vibrato.
• Slowly over an evening, always flat: new strings still stretching, or a guitar warming up in your hands and under the lights.
• From one day to the next, or one season to the next: temperature and humidity, and sometimes the neck itself.
• One string only: that string, its slot in the nut, its winding, or its tuning machine.
• All six together, the same way: the room, or a floating bridge that has tilted.

The five minute test

Guessing is how people end up buying new tuners for a problem in the nut. This test takes five minutes and points to the cause instead. Use the tuner right here: it shows the deviation of each string in cents, a cent being one hundredth of a semitone, and it keeps counting past fifty, so a string that has dropped a long way still reads as far as it really is.

1. Press Start and tune all six strings until each one sits inside the green zone, within five cents of its note. Always come up to the note from below.
2. Write the six readings down, or take a screenshot. They should all be close to zero.
3. Play for two minutes the way you normally play: a few open chords, a couple of firm bends on the G and B strings, the whammy bar if you have one.
4. Check every string again, without retuning anything first, and compare with your notes.
5. Read the result. One string moved: suspect that string, its nut slot or its winding. Every string moved the same way: suspect the room or a floating bridge. Nothing moved: your guitar holds its tuning, and the problem may be that it sounds wrong while in tune, which is a different diagnosis.

Why your guitar keeps going out of tune, cause by cause

1. The strings are new

This is the most common cause by far, and it fixes itself. A fresh set of strings keeps stretching after you put it on, and the windings around the posts keep tightening, so the pitch drops again and again for the first hours of playing. Steel strings usually settle within a few hours of playing. Nylon strings on a classical guitar stretch far more and can keep dropping for days.

You can get most of it over with in a few minutes. Tune a string to pitch, hook a finger under it near the middle and pull it gently away from the fretboard, about an inch, along its length. Retune, it will have dropped. Do that two or three times per string, then play, then tune again.

2. You are tuning down to the note

If a string is sharp and you loosen it until the tuner reads zero, the tuning often does not last. There is a little play in the gear of a tuning machine, and the string may be hung up in the nut on the way down. Loosen to the note and the slack is still waiting in the system; a few minutes of playing takes it up and the string goes flat.

The habit that fixes it costs nothing: always arrive at the note by tightening. If a string reads too high, bring it clearly below the target, then come back up to it. The tuner tells you which side you are on: too low, tighten; too high, loosen.

3. The room changed: temperature and humidity

A guitar is wood and metal, and both react to their surroundings. Steel strings lose a little tension as they warm up, which is why a guitar tuned in a cool room drifts flat under stage lights or after half an hour in your hands. Humidity moves the wood: the top and the neck swell or shrink, which changes the tension of every string at once and can change the height of the strings too.

The giveaway is that all six strings move together, in the same direction. The cure is patience: after bringing a guitar in from the cold or out of a hot car, leave it in its case for a while so it comes to room temperature slowly, then tune it. Tuning a cold guitar only means tuning it twice. If the seasons keep pushing yours around, a simple hygrometer in the room or the case tells you whether the air is the problem. Acoustic guitars suffer most; makers commonly recommend keeping them somewhere around 45 to 55 percent relative humidity.

4. A string is binding in the nut

The nut is the slotted strip at the top of the neck that the strings pass over on their way to the headstock. If a slot is too tight, rough or dry, the string sticks in it. You tune, nothing happens, you turn a bit more, and the string releases with a small ping and jumps past the note. The same thing happens in reverse after a bend: the string does not slide all the way back, and the note is off until something knocks it loose.

The first thing to try is graphite. Rub a soft pencil into the slot, or use a nut lubricant, and restring. If the ping is still there, the slot itself needs reshaping, and that is a job for a luthier: a slot filed too deep makes the string buzz, which is worse than the problem you started with.

5. The winding at the tuning post

A string that is wound loosely, in a bundle, or with the wraps crossing over each other keeps settling under tension and lets the pitch fall. Two or three neat wraps going down the post, with no overlap and no slack between the hole and the first wrap, hold far better. Plain strings, the thin ones, can use a wrap or two more than wound strings, because they slip more easily.

Check the other end too. On a steel string acoustic, the ball end should be seated firmly against the bridge plate under the pin, not resting on the side of the pin. On a classical guitar, the string tied at the bridge can slip until the knot tightens; a couple of extra turns in the tie usually ends it.

6. A floating vibrato

If your electric has a vibrato bridge, a Fender style unit or a Floyd Rose, the bridge floats in balance between the pull of the strings on one side and the springs in the back on the other. Everything is connected: change the tension of one string and the bridge tilts slightly, which changes all the others. That is why tuning one string takes the others out, and why dropping the sixth string to Drop D on a floating bridge makes the other five go sharp.

On a non locking vibrato, the usual culprit is friction: the nut, the string trees on the headstock, and the knife edges or pivot screws the bridge rocks on. If the strings cannot slide back after a dive, they come back off pitch. Lubricate the nut, make sure the windings are tidy, and tune in several passes over all six strings until they stop pulling on each other.

On a Floyd Rose, unlock the nut before tuning, set the fine tuners to the middle of their travel, tune with the machine heads in several passes, then lock the nut and finish with the fine tuners. If the bridge plate no longer sits roughly parallel to the body, the spring tension needs adjusting with the two screws in the back cavity, a quarter turn at a time, retuning after each move. A Bigsby has no locking at all, so it depends entirely on low friction everywhere the string touches.

7. Loose or worn tuning machines

This is the cause people suspect first, and it is one of the rarer ones. Before blaming the machines, check their screws: the small screw that holds each button, the nut or bushing on the face of the headstock, and the screws on the back. Snug them gently, without forcing. A loose button or a wobbling post can make a guitar seem hopeless and takes a screwdriver to fix.

A machine that is genuinely worn has play you can feel: you turn it and nothing happens for a moment, or the string creeps back down on its own with old strings and a clean nut. Then it is time to replace it. Locking tuners are a pleasant upgrade, especially with a vibrato, but they do not fix a string that binds in the nut.

8. The neck is moving

Last on the list, and the least likely. If the tuning drifts with the seasons, and the strings also seem to sit higher or lower than they used to, or start to buzz, the neck may be changing its curve. The neck has an adjustable steel truss rod inside it for exactly that. Do not turn it at random: have a luthier look at the guitar and do a full setup, which also checks the nut and the intonation while they are at it.

Habits that keep a guitar in tune

• Stretch new strings by hand before you start chasing them.
• Always tune up to the note, never down to it.
• Let a guitar come to room temperature in its case before tuning it.
• Keep graphite in the nut slots, especially if you bend a lot.
• Wind two or three tidy wraps at the post, no more, no overlap.
• Tune at the start of every session, then check again after ten minutes.

If you have tuned down for heavier music, check the strings too: a set that is too light for a low tuning goes floppy and wanders in pitch as you play. The chart in string gauge for drop tuning gives a starting gauge for each tuning. And if you are not sure your tuning method is sound to begin with, how to tune a guitar walks through it string by string.