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If I tune a guitar typically I see that I strike the string and the tuner records a certain value, e.g. dead on E. However often (maybe not always - but I can't say for sure) a few moments later the tuner shows that the string is tuned slightly below E.

What causes this? Surely as a string loses energy it doesn't drop in pitch?

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  • Maybe by tuning another string the neck gets slightly bowed and the string tension weakened.
    – Albrecht Hügli
    Dec 5, 2019 at 7:05
  • This may be a possibility - particularly if the guitar has a trem system. I will do some testing ;)
    – user307927
    Dec 5, 2019 at 13:03
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    May it be a duplicate?
    – wizclown
    Dec 5, 2019 at 15:43
  • Whilst you don't state what guitar you have, it's mostly a problem on 'cheaper' instruments. I have a mid 80s Washburn with Floyd-Rose trem, and it doesn't go out of tune when played for hours/weeks at a time. On the other hand, I've got a cheap-ish Telecaster that needs tuning every 5 minutes.
    – Neil
    Dec 5, 2019 at 16:15
  • Maybe not a strict duplicate, but the answers there pertain very much to here. Including the very important part about striking the strings while tuning to the same way you will be heard while playing. So my classical guitar and my steel string strumming guitar are tuned with slightly different techniques.
    – Guy Schalnat
    Dec 5, 2019 at 16:32

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I don't know the precise physics of this, but it's an expected phenomenon, especially on heavier strings.

When you first strike the string hard, the amount of displacement in the vibration from 'perfectly straight' stretches the string, so in effect raises its tension & therefore pitch.
As it gets quieter, that displacement becomes less, so the pitch drops slightly, back to 'nominal'.

If you strike the string more softly, or further back towards the bridge, this will happen less.

This is aside from anything you may accidentally be doing to the guitar as this happens, perhaps resting on the rear of the body whilst holding the neck, etc. or that as you progress through the strings, if all needed to be raised in pitch, by the time you get to the last string the neck will have pulled forwards slightly, making the earlier ones flat.

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  • Could it be that a hard strike actually does stretch the string slightly? It has to be 'pulled' tighter so it produces a higher pitch, before returning to its proper tension. By stroking it instead, it's more likely to 'stay in tune'.
    – Tim
    Dec 5, 2019 at 9:03
  • But surely if this were the case, as you strum a chord, for instance, it would sound out of tune as the volume decays. hmmm
    – user307927
    Dec 5, 2019 at 13:01
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    I'll add to this: it's well known amongst us bowed string players that the pitch sharpens slightly as we crescendo from p to ff . It's pure physics :-) .
    – Carl Witthoft
    Dec 5, 2019 at 13:06
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    @user307927 - if you hit it hard, it will, yes. It's all part of what makes a guitar [or any stringed instrument] sound 'alive'.
    – Tetsujin
    Dec 5, 2019 at 13:18
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    Yes. The “precise physics” of this involve two aspects: a) the “stretching” of the string. Actually, it's not stretching per se that's the problem – elastic stretching is the basis of why a string oscillates in the first place! – but that it's not perfectly linear: at strong amplitude the force becomes stronger than proportional to displacement. Solving this nonlinear differential equation yields a non-periodic solution, but its Fourier spectrum does indeed have higher frequencies than the linear low-amplitude version. b) inharmonicity.
    – leftaroundabout
    Dec 5, 2019 at 14:27
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Yes, this is expected, for the reason Tetsujin states -- that a string vibrating at a higher amplitude is under higher tension.

Of course this raises the question - do you tune the guitar so that the attack is in tune with the other instruments, or the decay? The answer may depend on what kind of part the guitar is playing, and the mix of the track. In many cases it will be too small a factor to matter much, but occasionally being mindful of the pitch envelope of the decaying string will help you improve your final recording a little.

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    There is another aspect to "being mindful of the pitch envelope" and tuning: since the effect is more pronounced for wound strings than for bare ones, and is more pronounced the thicker the strings are, it sometimes makes sense, at least in a studio recording context, to record the bass line first, and then tune the other instruments to a playback of the isolated bass track instead of to a tuner.
    – Jörg W Mittag
    Dec 5, 2019 at 16:44
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It's always going to be the case, when you play the string too hard. Think about it - the string is stretched slightly as you pluck it (more when you pluck harder), so the shown pitch is going to be higher. Once it settles down and is sounding normally, it's fine.

Way round is to not pluck too hard - the device should still 'hear' it, but in any case, wait a second to establish what the tuner has decided the note is. Then tune accordingly.

On a personal note, I'm increasingly dismayed that so many players rely so heavily on tuners that soon they may have lost any other means of tuning!! Wait till the battery goes flat!

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  • Don't forget tuning by ear is a skill that takes time to develop. My first guitar came with a tuning whistle, which made the learning curve even harder. Without a digital tuner I might not have made it past the first month. I do very much agree it's a valuable skill to learn.
    – MeanGreen
    Dec 5, 2019 at 10:45
  • @MeanGreen - too true. I threw away my tuning whistle, as it was out of tune!
    – Tim
    Dec 5, 2019 at 10:48
  • +1 for tuning by ear, especially if you have to play to a slightly out of tune piano! Always tune to the hardest instrument to tune in the group.
    – Guy Schalnat
    Dec 5, 2019 at 16:37
  • That said, if I AM the rhythm section for the session, and we are playing upbeat music with loud instruments, all anyone hears is my attack notes, so I tune to that initial strike, not the decay. It depends on the role of the guitar within the other instruments.
    – Guy Schalnat
    Dec 5, 2019 at 16:39
  • @GuySchalnat - that's maybe why I still prefer to do it aurally - a lot of '60s discs were around half a fret out from each other! What good would even a brilliant tuner (not invented yet) have been? Interestin that you tune slightly out. But if it works, it's a good move.
    – Tim
    Dec 5, 2019 at 16:39
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I was taught to tune from a higher frequency down to the correct value, instead of up from a low value.

There will likely be some difference in tension in the string, somewhere between the tuning mechanism to the nut after you stop turning the tuning peg. I assume the friction of the strings on the nut causes this.

It might not reveal itself directly, but when the tension evens itself out over the entire string later, the sounding part of the string can go slightly out of tune.

nut

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    Generally, the term 'tuning up' comes from the practice of starting lower and literally tuning up. Mostly pertaining to violins, cellos et al, but it is also applicable to guitars, which can slip down, but rarely slip up (I leave that for when I solo...). So starting with tension, and increasing it up to the desired pitch is what I've done for many decades.
    – Tim
    Dec 5, 2019 at 10:51
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    What's the pic for?
    – Tim
    Dec 5, 2019 at 11:01
  • @Tim for me the term 'nut' was new in this meaning. If it's clear to most people what part I mean I can remove it, but I'm not a native English speaker.
    – MeanGreen
    Dec 5, 2019 at 11:51
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    Now it's clear that the pic is to show 'nut' it makes sense. Good idea!
    – Tim
    Dec 5, 2019 at 12:10
  • The trouble with dropping to in tune from over-pitch is that the nut is far more likely to get sticky & suddenly drop 10 cents just when you thought it was all fine. Pulling on the strings as you would for a new string would help, but it's way more effort than just dropping the string a tone & tuning up from there.
    – Tetsujin
    Dec 5, 2019 at 19:23
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Most people find it easier to identify "in tune" when coming up from below. I dunno why; one of those neuroacoustic things.

There's the added advantage that you reduce the risk of snapping a string from overtensioning.

And equally important: tuning from below means there's no backlash or relaxation effects. If you tune from above, you are releasing tension but the string may well take a little time to fully release - hence drifting out of tune. And when tuning from below, the machine head (gears in the tuning mech) is always fully "non-backlashed" as well.

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  • I'm guessing because strings usually don't get more tight when you leave them alone. So in practice, you'll always be coming from below, adjusting to higher. Do that umpty years, and that's what you will get trained in.
    – Willem van Rumpt
    Dec 5, 2019 at 13:27
  • 'Tuning up' - true, but with violins and cellos, etc, isn't it to retain tension around the pegs. And have you tried those geared machine heads yet? Won't be long before Gibson gets their hands on them and automates them, as they have with guitars! Life will be so easy then - as soon as they go out of tune, the gears will re-tune for you!
    – Tim
    Dec 5, 2019 at 16:52
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What I usually do:

When I tune a guitar I pull on the string to stretch it or to control that it is correct fixed. Yes, and as I mentioned in my comment: Maybe by tuning another string the neck gets slightly bowed and the string tension weakened.

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  • Wouldn't that imply that effectively your guitar can't be tuned, and it's time to buy a new guitar? If tuning one string affects another string badly enough for the string to go out of tune, then you're basically doing a never ending dance to get it in tune. Worst case a very long and unreliable dance.
    – Willem van Rumpt
    Dec 5, 2019 at 16:36
  • @WillemvanRumpt - it's fairly standard procedure on a full restring, especially if you have a skinny neck like an SG, or a floating trem. Quick tune from bottom to top, then an accurate one correcting the inherent detune the first one generates.
    – Tetsujin
    Dec 5, 2019 at 19:19
  • @Tetsujin: Yes. On a full restring.
    – Willem van Rumpt
    Dec 6, 2019 at 6:52

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