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I understand how Guitar works. Pitch/Frequency of sound produced depends on length of vibrating string. So we have different frets to product different notes. Fine.

However I am curious to understand how the fret itself is designed. When finger moved to new fret we hear new sound. But within the same fret, even if finger is in different position (so here length of vibrating string changes) we hear the same note. Why and how? How Frets are designed in such a way?

If it is just natural, then are music notes discrete? I believe classical musical like Indian Carnatic music assumes music notes are continuous. So I don't think music notes are discrete, instead Guitar frets are designed in such a way to make it sound discrete. Please advise. Thank you :)

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    To raise the pitch of a string, you must shorten it. So look at the fret. Press down on the string inside a fret and see how the fret bar shortens the part of the string you play. Then move your finger around inside the fret. There is no mystery here. You can see what's happening quite clearly. – Apologize and reinstate Monica Aug 9 at 20:17
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    @only_pro - and what is happening so clearly? – Tim Aug 10 at 4:06
  • @Tim OP is supposed to try it and see. That's why I didn't say it. But, obviously, and as I'm sure you already know, the fret bar keeps the string the same length. – Apologize and reinstate Monica Aug 12 at 16:26
  • @only_pro - true, the string will always be the same length from the same fret. What I tried to explain in my 'slightly misaligned' answer is that due to the amount of pressure applied on that particular fret, the note itself can and will change in pitch, which is not what OP thinks. – Tim Aug 12 at 16:41
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Actually, this is asked using inaccurate facts.

The position of the fingertip within the space of two fretwires does produce a note - but the pitch of that note does vary considering where in that space the finger is. That's how we get vibrato - classical style. By rolling the fingertip towards and away from the bridge, within one fret space, the note changes, albeit slightly.

That aside, the premise is that wherever the string is pressed on a particular fret space, the note is the same. That's because the string will sound from bridge (or saddle) to that fretwire. It's always the same distance, so will always be the same note. Essentially.

There's also the fact that within a fret space, extra pressure can be applied. This will sharpen a fretted note. It's how one student of mine makes vibrato.

The essence of frets is that it splits the fingerboard into discrete diatonic parts, and well made fretboards will (basically) mean the same note gets played on the same fret on the same string every time - assuming the guitar's tuned properly!

There are fretless guitars - just like there are fretless bass guitars - but while they are far less easy to play in tune, due to inaccuracy of fingering as the fretwires aren't there to help - they behave more like the violin family, consequently are more able to play some note with more accuracy than those compromised by being fretted.

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    Going by the response, you haven't. I am not saying that for eample, if a finger is half-way behind a fretwire that the note is halfway between that and the lower semitone! – Tim Aug 9 at 9:10
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    What? The second paragraph is not how any of my guitars work. – Todd Wilcox Aug 9 at 12:40
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    When I make vibrato on a nylon string guitar, it’s by stretching and contracting the string. When my finger moves away from the bridge, the string is pulled tighter, raising the pitch. When my finger moves towards the bridge, the string is loosened, lowering the pitch. My vibrato technique on steel strings is not unusual: I wiggle my finger(s) up and down. This can only raise the pitch and return it to the fretted pitch, but again it’s very common. The reason why I and most others don’t try the nylon technique on steel string is there is less friction to pull and push and it would be painful. – Todd Wilcox Aug 9 at 13:33
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    Without the friction and stretching/contracting of the string, any finger position between the frets should produce the same note (barring pressing down harder towards the fretboard). This can be tested by simply lifting and replacing the finger at different places between the frets with a tuner running. – Todd Wilcox Aug 9 at 13:35
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    The tension in classical vibrato is not raised by the position of the finger. It’s raised by pulling the string tighter. For me, rubbing my finger back and forth on a .010” diameter steel string would just cause the string to cut into my finger. Hence pain. – Todd Wilcox Aug 9 at 14:11
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Actually music notes are not discrete. The guitar, like the piano, is designed to have equal tempered tuning rather than just tuning. In that tuning system notes are discrete, half step = 12th root of 2. Even in just tuning we only have 7 notes in the diatonic scale but we are free to make slight deviations and some cultures do use quarter steps (a half of a half step) in their scales.

As for where you place the finger, there is a "correct" way to do this. The finger should be placed just behind the fret. This is to avoid letting the string slide or slap against the fret as it vibrates. If you fret the note with your finger somewhere in the middle of the space between frets you are not really creating a boundary condition between the bridge and the fret. The string is not truly "fixed" at the fret. If you don't overdrive the string mechanically it wont matter but if you play with too much force the string will not stay fixed at the fret but slide along it, even lifting slightly and slapping down on the fret. This will cause buzzing and a sitar like sound. This is a bigger issue on the classical. When you have complex chords forms we sometimes have no choice and simply need to get a finger somewhere in the space but if we can, we should get them pinched right behind the fret. Along the same lines a common misconception is that the string needs to be pressed down to the wood of the finger board. This is also not true. Only enough pressure is required to stop buzzing against the fret and get a good tone. In theory one should be able to slide a piece of paper under the string even when fretted. This is as true for the electric as it is for the acoustic or classical but not as necessary. In my experience the electric is a little more forgiving (if set up well). If you do press the string down to the wood you will bend it our of tune. If you experiment, playing just one note varying all these different parameters you will hear it.

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    I have a Telecaster with Large frets and have to be careful when fretting not to pull the strings all the way down to the wood. Doing so will pull the string out of tune, but I like it for string bending when I'm playing. I think it's about the same as having a scalloped fretboard, I just need to pay close attention when I'm playing it. – skinny peacock Aug 9 at 18:27
  • Yep, not need to damage the wood with high frets. – ggcg Aug 9 at 18:29
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Why and how? How Frets are designed in such a way?

If you actually have a guitar in your hands, it's very obvious how frets work. The fret is raised above the fingerboard, so if you place your finger behind a fret, the string will become 'stopped' at that fret such that the 'speaking length' of the string is the length between the bridge and the fret. Here's a simplified diagram showing a guitar with one fret:

guitar with one fret.

From your deleted answer:

I got to know now how it works. So Frets do have a divider between them. So whenever fingers press against a fret, whatever finger's position within the same fret, it is this divider which gets in contact with string so length of vibrating string doesn't change, except when fingers moved to new fret new divider will come into play.

You got the idea ok, but 'fret' is the name for the 'divider'.

If it is just natural, then are music notes discrete? I believe classical musical like Indian Carnatic music assumes music notes are continuous. So I don't think music notes are discrete, instead Guitar frets are designed in such a way to make it sound discrete.

That's quite a complicated question! In most contexts in western music, notes are assumed to have a single particular pitch, but it's also understood that they can be bent, or that effects like vibrato or glissando can be used to change the pitch. A fretted guitar can't easily do a glissando, but it can do bends and vibrato through the mechanisms described in other answers.

  • "If you actually have a guitar in your hands, it's very obvious how frets work." I was wondering the same when reading the question. – Džuris Aug 10 at 15:43
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The pitch of the note (frequency of vibration) is set by (at least) 3 factors;

  1. the length of the vibrating portion of the string,

  2. the mass of the vibrating portion of the string, and

  3. the tension of the string.

So:

  1. The vibrating length of the string between fret and saddle remains the same, regardless of where you fret. The frets are intended to make the notes discrete.

  2. I don't know of any way to change the mass of the strings on the fly.

  3. Varying the tension, like by bending or pulling the string or bending the neck, will change the note.

Hmm, would the stiffness of the string material affect frequency as well?

  • - no. It would affect the amount of effort needed to change the pitch, that's all. – Tim Aug 9 at 17:33
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    Your comment for (1) is not completely true. The effective length does change because the boundary is not at the fret if you finger it too far behind the fret. This is a pretty well known fact. – ggcg Aug 9 at 18:26
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    Sorry, not sure what you mean. On my guitars, no matter where I put my finger (even just after the previous fret) the fret is still the boundary. Maybe I'm misunderstanding this... – Kermit Brown Aug 9 at 19:54
  • No it isn't, it definitely is not just based on physics. – ggcg Aug 9 at 21:10
  • Stop fighting kids, everyone is right. ;) It will depend on how "high" or "outwards" is the fret. If it's "lower" (closer to the board) then putting your finger far will make a difference, but if it's "high" (a more prominent bump in the fretboard) then it's possible that even if the finger is almost at the next fret the string will still be stopped at the previous fret. ;) – msb Aug 10 at 17:18
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There's a bit of trigonometry involved, but there are at least three effects that can slightly change the pitch due to the finger position and pressure between frets.

Here's one:

Three points, the tops of two frets and a spot on the fret board between them and below them in height makes a triangle.

The shortest distance of the two straight lines between the fret tops and the fret boards are when they are equal, e.g. when the finger pressure position is exactly between two frets. Any other fretted geometry results in a slightly longer total distance of those two line segments. e.g. if you press near the fret nearest the bridge, then the triangle distance will be slightly longer. To provide this longer length, the whole string has to be stretched more. Stretching a string creates a higher tension. And tension (as well as length, diameter, and distributed weight) is one of the things that effects the stable vibrational modes of the sounding portion of the string, e.g. pitch frequency.

Secondly, the finger pressure that frets the string does not always have to take the string all the way to the fret board, but just enough to keep the string from vibrating off of the fret. Additional pressure could again change the length of the string segments between frets, either lengthening and/or increasing tension along the vibrating portion.

The third effect can be created by moving the string slightly sideways across the fret during the fretting. This slight angle offset can slightly lengthen the distance between the fretted point and the bridge, both stretching and lengthening the strings, which again will affect the stable vibrational modes.

Either or multiple of these can be modulated by finger position and pressure. And exactly when they are modulated, either during the pluck transient or the stable sustain portion of evolving string motions can also have different affects on the timbre, as well as the perceived pitch.

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