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I am still very new to learning guitar (specifically, Classical fingerstyle). While this is the first time I am doing this "seriously", I HAVE tried to learn guitar before, just very badly (and usually with crappy instruments that have been handed down and mistreated by family). I am currently using a tuner app on my phone, although I just ordered a nicer clip-on tuner (Snark SN-2). In the past I've used other mic'd chromatic tuners.

I'm just curious why it is, when tuning, that when you get a note "perfect" it's only exactly in tune for a moment after the string is struck. After that moment, the tuner starts to frequency wobbling sharp and flat around the ideal tuning.

What causes that to happen? I've read a bit about tuning now trying to find out, and everyone just seems to repeat that it's the note played originally that has to be as close to exactly in tune as possible, and not to worry about afterwards.

What confuses me is that the string length never changes, so the wavelength shouldn't change. The frequency may slow down as the string stops vibrating as fast... but why would it sometimes go up too? Maybe I'm thinking about it wrong?

Wouldn't this affect sustained long notes, or is it mostly imperceivable by the ear?

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There's a wide range of opinions on how often to use a visual tuner while playing. I'm firmly in the "don't use it very often camp". Remember, music isn't notes written on a page or a wavy line on the tuner- it's sound. Follow your ears at all times (not just when you're tuning before you start playing) and you'll always be in tune. –  musical_coder Sep 4 at 4:49
    
Just for one aspect: the frequency changes not only with length of the string (even this is the most visible factor), but also with the tension. Tuning a guitar string will not change the length, but only the tension. I don't assume your are interested in the formula? –  guidot Sep 4 at 6:57
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@musical_coder: I believe tuners were invented precisely due to the fact that not all people have a good ear and can tune properly. Tuning is also quite tedious to listen to. While obviously one should use one's ears, a diatribe against tuners isn't likely to a) be heeded or b) make progress for music in general. –  Meaningful Username Sep 4 at 9:18
    
@musical_coder easy to say, but I can't tell by ear if something is in tune or not so I find a visual tuner useful! –  Matt McNabb Sep 4 at 11:28
    
It's fine to use a tuner to get your ears started in the right direction, but just wanted to make the point not to let a visual tuner be the end-all. People sometimes forget to wean themselves off of it. I agree that overall, this is a good question to ask about tuning and the physics of sound. –  musical_coder Sep 4 at 12:57

6 Answers 6

Plucking a string increases its tension momentarily. This tension drops rapidly as the vibration dies out. This causes the pitch to drop slightly as the string vibrates. It's an inherent limitation of plucked string instruments but it's OK, it's part of the sound we know and love.

Also, unlike the ideal mathematical model, strings vibrate in two dimensions. Since the change in tension is more pronounced in one dimension than the other, we're actually hearing two sounds. This causes some harmonics to get cancelled while others become more pronounced. As the frequencies of these two vibrations shift relative to each other, the harmonics that get cancelled or become pronounced also change. This causes a slight chorusing or flanging effect. It's also an inherent limitation of plucked string instruments but it's also OK, it's also part of the sound we know and love.

Digital tuners are not perfect. These changes in harmonic distribution and drop in volume cause them to misread the exact pitch. This is probably the reason why you see some "wobbling" that follows the initial pitch drop.

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can you elaborate on how to pluck or how to interpret the digital tuner's output in order to get as close to the exact pitch as possible? –  Matt McNabb Sep 4 at 11:29
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FWIW, tone drop occurs with bowed instruments as well once the bow is removed from the string. The tone can sharpen as the bow forces a crescendo, too. –  Carl Witthoft Sep 4 at 11:45
    
@Matt: try gently resting a finger of your left hand at the half-way fret and releasing as the string is plucked. This mutes some harmonics and can give a tone that is easier to tune. –  RedGrittyBrick Sep 4 at 12:55
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@MattMcNabb Plucking the string as gently as possible will make it less sharp. Also, plucking it near the middle of the string will emphasize the fundamental note more and overtones less, which will create less confusion for your tuner. On an electric guitar, rolling off the tone knob also helps. –  Bradd Szonye Sep 8 at 22:49
    
A rather nice demo is to hang a piece of string so it hangs between two points with a slight sag in the middle, tie another piece of string to the midpoint of the first, and hang a small weight from the second, and start it spinning in a circle. The rotation will subside as the weight shifts toward swinging in a diagonal line, then the rotation will reverse, then the weight will swing on the other diagonal, etc. Something similar can happen on the guitar since the ends don't restrict vertical and horizontal movements quite the same way. –  supercat Oct 23 at 2:37

You should tune it a little sharp not just the exact note, because this is going to happen over and over again.

Why?

tuning peg

because the tuning pegs use to turn by their own (it depends on the quality of the gears), you can't notice it because it takes time, take in count that you add tension to the strings every time you play.

I hope this helps

BTW if you are learning, like me! I give you and advice. take this course https://www.coursera.org/course/guitar is free!

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IF your machine heads are moving on their own, you need to repair or replace them. This is not natural -- assuming you're not mistaking the up vs. down hysteresis in the gearing. –  Carl Witthoft Sep 4 at 11:46
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If you tune sharp, you are out of tune with anyone else who isn't tuned sharp. If your instrument drifts flat, that just means that you need to retune more often, and as Carl said, get your instrument repaired. –  Karen Sep 4 at 13:13

I've noticed a drop in tune in two places when I change my strings. 1: After I change a string and move on to the next one. 2: It drops again after I cut the excess string off after I'm done changing them all.

I've found that after getting the string to pitch, tune it up a half-step and some change. This helps compensate the loss on my electric with standard gibson bridge and my Blueridge acoustic.

Hope this helps. Now go play!

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The fact you have picked up on this shows you have a good ear, here are some tips to make your guitar ring like an angel :)

Make sure you have a good tuner that is accurate, (doesn't have to be expensive). Read plenty of reviews on it don't just go buy one.

Always tune turning up, if you overshoot go back and start again. This makes sure there is no tension unreleased, more so for older strings when they start to click when tuning.

Tune at temperature, tune it so you can play without irritation, then tune again once you have warmed up the guitar. (don't annoyingly tune in front of people, unless you have a muting tuner)

Tune according to playing style. If you are going to be picking really hard and quickly, the note that stands out the most is the one you want to tune for. If you need lots of resonance then its the ringing I tune for.

How long after picking, My favourite spot to tune to is about 1 second after picking it medium to gentle. No earlier as its to sharp, no later as it starts to go flat.

.

--Expert Level--

If your guitar is tuned well, keep tuning it and let the other strings resonate (i.e. don't mute them). You will hear a rise and fall (like a wobbling) in the volume of the harmonics (the high pitched ringing noise).

You can finer tune by aiming to reduce the speed it rises and falls. Sometimes I've re-tuned my guitar, with my tuner saying every string is in tune both before and after, and can still hear an improvement! Other times I have tuned a guitar so the tuner says its slightly out of tune, but it sounds better with my tuning because it is tailored to the guitar. Although this improves lots of open string and low down chords, it can make higher up notes slightly out of tune. (this is purely open string, not the harmonic tuning method).

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I've noticed this and I really think it's simply due to the fact that over time the loudness of the note tapers off, so the tuner is less able to accurately pickup the tone with its microphone.

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An important factor is the loudness of the string. This done'st change the note, of coures, but the tuner will be only sensitive to so much of the string's "note life"- that is :

You pluck the string. The attack in the note tells the tuner to start 'listening' for a note.

The tuner can gather something while the signal is clear and strong

As the note dies away (quickly on a classical guitar), the tuner can't get a clear signal anymore, as perhaps other backgorund nopises start to interfere, and the tuner starts to wonder.

So you're likely to get a good reading while the note is loud, and less so as the note dies away. On an electric guitar with plenty of sustain, this "moment of clarity" can be many seconds, but on a classical guitar with nylon strings, the decay can be much quicker.

Also with an electric guitar, outside noises play no part because the connection is electric, not acoustic. With a classical guitar, you're presumably using the mic in your phone (or tuner) to gather the note, maining it'll pick up other noises.

The clip-on tuners use vibration instead of a microphone. My experience (a Snark) is that these go a long way towards helping with background noise as the vibration is more clear.

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