Why Acoustic Guitars Go Out Of Tune

Keeping your guitar in tune is a chore that never really goes away, even the seasoned professional musician who knows every factor that contributes to tuning instability still has to deal with this frustrating issue.

But it’s even worse if you are a newer player and can’t find out what exactly is causing your guitar to go out of tune. While some things a local guitar technician can help with, others you just need to be aware of and can introduce some simple practices into your string changing/cleaning routine to help keep your guitar playing as well as it possibly can.

“Take care of your instrument and it will take care of you”

So today we’re going to cover all the primary contributing factors that will make your acoustic guitar difficult to keep in tune.

Table of Contents

Old Strings

Old strings are usually the first thing people will mention when it comes to dealing with tuning issues, and you’ll quickly be encouraged to swap them out for a new set to solve many of your common pitch-related woes.

The factors that play into this are often quite subtle, but over time they can accumulate to some fairly noticeable tuning issues.

As we play guitar strings, despite our best efforts to keep them clean and wipe them off after each play session (you are doing that, right?) they will slowly build up oils, dirt, and grime. The acids on your hands will oxidize and corrode the string, the rubbing against the frets and the pick striking the strings.

All these things can be broadly summed up as ‘wear’ on the string, and irrespective of the loss of tone, that damage can cause tuning issues, particularly when it comes to intonation.

You might find your open E note rings out just fine, but by the time you get up to the 12th fret, it could be as much as 50 cents out of tune!

On acoustic guitars, this is particularly hard to address as bridge adjustments are not a simple turn of a screw away.

The simple solution to this is just to put some new strings on your guitar. There’s no pre-determined schedule when it comes to how often you should change strings. Over time you’ll get a feel for when the tone starts to sound dull and it becomes more difficult to keep in tune. Use that as your cue to swap them out.

New strings

Then as soon as you put new strings on you’re immediately faced with a new issue! But don’t worry, this one’s much easier to deal with.

Guitar strings stretch a lot, particularly when they are new. And although some manufacturers will pre-stretch the strings they will inevitably still stretch once brought up to pitch and under full tension.

The simple solution to this is after you have tuned your instrument, lightly pull up on the strings all the way from the nut to the bridge, do this on each string to help work that extra ‘give’ out of them.

Once you do that you should find everything is flat, tune it up again and it should hold its tuning much better! If not repeat this exercise 2-3 times and your strings should start behaving.

Incorrect intonation

If you find that even though your open notes are tuned perfectly, as you climb up the neck it slowly gets more and more out of tune, there’s a good chance your guitar’s intonation is off.

On an acoustic guitar, we don’t have individual bridge saddles to control intonation, they use much more of a “set and forget” kind of construction. So what you can do here is visually check the bridge to see if it’s seated correctly, or if it is leaning forward or backward? Has the glue worn down which has made it lean a particular way?

Unfortunately, this is oftentimes not an easy DIY fix, and unless you are already quite confident with what you are doing we recommend taking your guitar to a local store to let their guitar technician take a look at it.

Tuning pegs

Martin acoustic guitar headstock, strings and tuners

There are 2 main reasons why the tuning pegs contribute to tuning issues, and they’re both equally as common.

The first is because something has come loose. Usually, a screw which is allowing the tuner to rotate outside of the intended mechanical movement.

Every time you change strings and clean your guitar, we recommend giving all your tuning pegs the once over and just making sure all those screws are tightened down.

The other factor is just generally low-quality tuning pegs, they might naturally slip, and maybe they don’t hold the string properly. Sometimes upgrading the tuning pegs on your instrument to higher quality ones can increase your tuning stability.

String Slippage

There are two things to keep in mind when attaching a string to a tuning peg that will give it the best possible chance of keeping in tune.

1: Don’t overwind the string

Manufacturers will often give you a ton of extra string to account for things like baritone instruments. You don’t actually need to use all that excess, and winding the string too many times around the tuning peg leaves extra material that, over time, will continue to stretch. This can give you the prolonged issue of the string consistently drifting in its tuning.

The solution to this is to use the smallest number of windings possible so there’s as little material there to continue stretching and slipping over time. We recommend 2 to 3 winds around the peg for an acoustic guitar. Then just trim the excess off with some clippers.

2: Wrap the string

Acoustic guitars don’t generally have anything mechanically in place to lock the string into the tuning peg, it usually just relies on the tension of the string to hold it in place.

But these are smooth strings held onto a smooth tuning peg, they will inevitably slip over time. One possible way to counter this is to ‘wrap’ the string over itself when re-stringing to essentially emulate what a locking tuner on an electric guitar aims to achieve.

To do this you thread the string through the peg as normal, but then turn it around and feed it over, then under where the string first enters the peg. Then tune it up to pitch as normal.

This will act as a ‘lock’ to keep the string held in place and stop slippage.

Worn out or incorrectly cut nut

The nut sits right at the base of the headstock and acts as 1 of the 2 termination points for string vibration.

To ensure the string vibrates perfectly between the nut and the other termination point (the bridge) which is paramount for the string to vibrate at the correct pitch and produce the correct note, it needs to fit that string nicely and snugly.

As people like to experiment with different tunings and string gauges you will quite commonly find the nut to be the culprit of some tuning issues for 2 main reasons.

The slot not being the correct size to fit the string

If the nut’s ‘slot’ can’t quite seat the string it will end up being suspended in the air just being pinched on either side, which results in a whole host of tuning issues.

Primarily because when a string is ‘suspended’ in the nut, it’s actually lengthened the string slightly which is going to make it impossible to intonate and tune correctly.

Not only that, but it’s also going to make your string action higher. Which just, in general, will make your instrument more difficult to play, but that additional travel time the string takes to reach the fret adds additional tension to the string, making notes go sharp.

Needless to say, making sure the string is seated snugly in the nut is pretty important!

Tight Nut Slots

Another issue this causes is if the nut doesn’t provide a smooth surface for the string to travel over.

This is where you tune your string up, and up, and up, and it seems to not change pitch, then suddenly you’ll hear a PING, and it’s now completely sharp. This is because the nut is gripping the string and not allowing it to raise pitch smoothly, it’s only when the tension is too much that the string will break free of the nuts grip, and by then you’re already too sharp.

You can use ‘nut oil’ to help lubricate the nut and help the string travel smoother within it, although this needs to be used fairly infrequently as going overboard here will just gum up the strings. Another option is to use graphite to lubricate the path for the strings. To do this simply take a sharp pencil and run it between the nut slots as per the image below.

Temperature and humidity

This one is hard to avoid, but keeping aware of its effects can help to inform you of why your instrument is struggling to hold its tuning.

High temperature and high humidity will make wood expand, likewise, cold weather and low humidity will make it contract.

So traveling, or getting the guitar out from cold storage and suddenly standing on a hot stage is going to wreak havoc with the stability of the instrument.

There’s no real magic trick with this, just use common sense. If you know your guitar has been in a cold place give it some time to come up to temperature and adjust before tuning it.

Humidity can be much more difficult to control and is particularly important when storing your instrument. If you store it in a place with high humidity for too long your acoustic can suffer some real issues such as the bracing or neck warping.

Some people get very meticulous with managing humidity, but I’d just recommend if you know the place you most commonly store your guitar experiences high humidity. Consider sticking a dehumidifier in there to manage it a little.

Strap

Some acoustic guitars have the strap attached to the headstock, and no matter how well built your instrument is, the weight your arms exert on the instrument as you play essentially makes that strap act like it’s pulling up on the headstock.

This can very easily bend the neck and make notes go sharp. Where possible it’s best to have your straps two points of contact attached to the body as it’s a much more robust and stable location that’s less susceptible to bending.

Poor capo placement

A fairly easy one to solve, but it’s also one that if you aren’t aware of it can be the cause of some major headaches!

The capo should be placed right behind the fret, it can even be touching the fret ever so slightly.

The main reason for this is because when the capo is placed in the center between two frets, the pressure provided by the capo can actually make the string ‘sink’ into the fret more, which makes every string go slightly sharp.

This effect is essentially nullified when the capo is moved right behind the fret wire itself as it acts as a support for the string to stop the capo from depressing it too much.

Technique

Much in the same vein as the capo issue, if you press too hard on the strings or are unintentionally bending the string up when holding some particularly awkward chords. This will result in your acoustic going out of tune, usually sharp.

So try to keep an eye on what your hands are doing and look for any scenarios in which you might be disturbing the natural ‘line’ of the string.

Only tune up, never tune down

Finally, we will leave you with a good general practice which is when you tune your instrument, only tune it up to the pitch from below.

If you accidentally go sharp and need to flatten the note, flatten it to quite a bit below the target pitch and then go again and approach slowly tuning up to pitch from below.

The main reason for this is tuning down creates slack in the string and around the headstock, and no matter where you land as you play and work out that slack from the string you’ll find it will continue going flat.

You don’t get this issue when tuning up. So a good rule of thumb is to tune down 1 semitone below your target pitch, give the string a little tug if you want to help work out that extra slack, and then slowly bring it up to pitch.

Final thoughts

So as you’ve no doubt gathered there are a lot of factors that can contribute to your acoustic guitar going out of tune.

While you certainly don’t need to commit all the information shared here to memory, it’s worth keeping this as a handy guide so if at some stage you find yourself faced with tuning issues you can reference back to this and hopefully find a solution to your particular issue!