Like every classical guitarist on the planet, I too have observed that a new set of strings does not stay in tune for long. It needs constant adjustment over days if not weeks. I sought out forums and expert sites to find out why this happened and how to manage the problem, if not avoid it totally.
Why do classical guitar strings go out of tune? Classical guitar strings are basically nylon filaments with inherent elasticity. They stretch with tightening. The pitch increases immediately, but it can take a day more for the strings to fully stretch out. With this additional stretching over time – the actual physical lengthening of the string – the pitch gets lower. Which is why the notes sound flat within hours of a new set of strings being set to tune.
As you fix and tighten a new set of strings, you not only add tension on them, you also make them stretch. This is why when you pick up the guitar the next morning after fixing a new set the previous evening that the notes sound flat. Since plastic (nylon) is more elastic than steel, classical guitar strings tend to be more unstable in this respect.
Which is also why some solutions that work so well on a steel strung guitar do not always work with the classical guitar. More on that soon. Since it is in the nature of nylon strings that they go out of tune more often and require frequent adjustments to bring them to tune, you have to some extent accept the beast for what it is. You’ll have to get used to tuning it frequently.
But there are solutions to consider. You may not defeat the beast but you can tame it, keep it largely in check.
Other causes for a classical guitar going out of tune
In all but extreme cases, there is likely nothing wrong with your tuning machines or your guitar. In general that is a good thing to keep in mind – unless you are pulling out an old relic of a guitar from the attic and trying to refurbish it. Assume your guitar is good.
Change in heat and humidity: Heat and humidity changes affect string tuning measurably. If you pulled out a nice, cool guitar from its case in a somewhat chilly room, the heat from your body will warm up the guitar as you play. Heat expands wood. Of course you can’t see the guitar getting visibly bigger. The expansion is real nevertheless and changes the distance between the nut and the saddle by a tiny amount. That’s all it takes to get the guitar out of tune.
The G string is the thickest nylon string and much more temperature sensitive than the other two.
The act of tuning itself: Tuning the guitar in itself will actually cause the strings to go out of tune. For example, if you pick up your badly out-of-tune guitar and tune all 6 strings and then you play a chord or two you may notice that the instrument is out of tune. By the time you’ve completed tuning all six strings, the increase in tension is often large enough that some of the strings are again noticeably out of tune. By the time you finish the tuning on the last string, the earlier ones have expanded and gone out of tune.
Especially during the first few days of installing a new set of strings, classical guitars go out of tune very rapidly, Many players avoid changing string sets especially before a coming concert. As noted, due to their high degree of internal elasticity, it takes time for the strings to settle in.
Improper winding: It might be the strings themselves, or more precisely the way they’ve been affixed. Loose windings on the tuning pegs and/or slack in the wraps at the bridge are common causes of a guitar rapidly going out of tune.
Solutions to correct out of tune strings
String stretching: If you already know of this method, you will either be nodding your head approvingly or banging your head in frustration at the amount of disinformation on the inter webs. It has become a controversial ‘solution’ in recent years, even though this is a regular and standard solution in the world of electric guitars. Guitar techs for rock artists and string manufacturers for steel strung guitars routinely advocate string stretching while fixing a new set.
But classical guitarists – a rising number of them, lately – question this method vehemently for use on the more ‘stretchy’ nylon strings.
The actual act of string stretching is simple enough. When you install a string, manually stretch it out. Put your hand palm-up under the string (or all strings at once, which is what I do) approximately over the twelfth fret and lift them a few inches above the fretboard. You’ll feel them stretch. You will probably never get the tension high enough to snap but be reasonable and don’t over-stretch. Repeat the stretching action two or three times, no more.
The theory is if you now bring the string or strings into tune (or, by some advocates, a semi-tone above the intended pitch) they won’t stretch any more because you’ve already stretched them with the lifting. No less a company than the reputed string maker Aquila has a video on the subject of fixing new strings showing the stretching action.
To make the strings “become stable faster, pull it at the 12th fret during installation, repeating it until the tuning variation after each pull gets minimum. The strings need a few days after first installation to develop their full sound, so we suggest to install them and then wait at least an overnight before using them professionally.” See the Aquila video below for the demonstration.
How to install Aquila Nylgut strings
Many of the knowledgeable folks in the Delcamp forums find string stretching a questionable practice. A classical guitar is much more lightly built than a steel string, they say, and to stretch the strings in this manner while they are attached to the guitar could greatly increase the tension and put a lot of strain on the bridge/top of the guitar.
Pre-stretching nylon strings like on a steel string guitar is a bad idea, they believe. Nylon strings that are over tuned or stretched by pulling on the strings can stretch unevenly across the length, causing intonation problems.
They have a point. I have seen an amusing video on guitarist and teacher Douglas Niedt’s site which is titled How to Ruin a String. He basically ruins a perfectly tuned first string by stretching it! The stretched string suddenly develops intonation issues where there were none before. (The video is meant for subscribers only, so you may not be able to access it.)
You are free to take your side on this debate. As a non-scientist who does not understand the subtleties of elasticity of substances (and other related mumbo-jumbo), I take the conservative view. I would not stretch my string based on the horror stories I’m hearing from advanced players.
Douglas Niedt, who is also my guitar tutor, talks straight and calls a spade by name and he has over 50 years of playing experience in concerts and teaching. But then, that’s me.
Tuning up by a semi-tone: This is a useful trick while fixing a new set of strings. If you tune them up for the first time and only tune them to the “correct” pitch they’ve still got a lot of stretch left, so the string immediately starts stretching (getting longer) and the pitch gets steadily lower. The best thing is to tune them up an additional half-step and over the next day or two, just tune up that extra half step each time after you’ve finished playing. They’ll settle in fairly quickly that way.
Also, properly tuning a guitar usually requires at least two passes. After tuning all 6 strings to pitch, you must tune them once again. On the second pass, the strings will need only a little bit of fine tuning.
Beware of over tuning though. Over stretching by a whole tone or more can cause intonation problems by creating thin spots along the length of the string. Some prefer not to tune the strings any higher than their working pitch but just keep the guitar out and tune to pitch every 30 minutes or so. The strings, they find, settle sufficiently in a day.
Frequently tuning a new set of strings: When I change my strings, I keep re-tuning the guitar every few minutes (while watching TV). The following day I will take the guitar out of its case every couple of hours and re-tune it. I just keep re-tuning frequently and in a couple of days all that is needed are micro-adjustments.
Doug Niedt says: “For the casual player, tune them before and after every meal, before you go to work and after you return, and before bedtime.”
Using carbon trebles: A carbon third string, if not a set of 3 carbon trebles, will help because carbon is much less sensitive to temperature variations. Savarez Alliance, Knobloch Carbon are among the many brand options available. They take longer to settle initially but once stable, you will not see much tonal variation with temperature. (Catch up on what’s so great about carbon strings; read my piece Try Out Carbon Strings On Your Guitar.)
The third string being the thickest of the trebles tends to show intonation problems the most in many players’ experience. Some prefer titanium trebles. They come up to pitch much more quickly than nylon or carbon trebles.
Fixing strings at both ends correctly: Personally, I string the guitar in such a way as to minimize wraps on the tuning rollers. Because the whole length of the string stretches – including the bits wound on the rollers – if you minimize those, you cut on the time of significant initial stretching. Making fewer turns around the roller helps a bit too.
Nylon strings do stretch, but they also slip almost just as much. If you are careful about tying them on both ends and keeping as few wraps as possible on the roller, they should stay in tune pretty well the first or second day itself. Securing strings properly to ensure that there’s no slippage is probably key.
Related topic: Why does the G string always sound so bad? Read it to understand why and more importantly know what you can do about it.
Related topic: Why do strings slip? Carbon and titanium trebles, in particular, slip and lose tension when you’re fixing them. What should you do to prevent this from happening?
Related topic: Intonation issues. Check with this article to identify intonation issues with your guitar and how to set them right.