0:00:07.014,0:00:10.777
Hendrix, Cobain and Page.

0:00:10.777,0:00:12.354
They can all shred,

0:00:12.354,0:00:16.235
but how exactly do the iconic [br]contraptions in their hands

0:00:16.235,0:00:21.694
produce notes, rhythm, melody and music.

0:00:21.694,0:00:26.603
When you pluck a guitar string, you create[br]a vibration called a standing wave.

0:00:26.603,0:00:30.530
Some points on the string, called nodes,[br]don't move at all,

0:00:30.530,0:00:35.180
while other points, anti-nodes, [br]oscillate back and forth.

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The vibration translates through the neck[br]and bridge to the guitar's body,

0:00:39.584,0:00:42.432
where the thin and flexible wood vibrates,

0:00:42.432,0:00:46.625
jostling the surrounding air molecules[br]together and apart.

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These sequential compressions[br]create sound waves,

0:00:49.730,0:00:53.932
and the ones inside the guitar[br]mostly escape through the hole.

0:00:53.932,0:00:56.221
They eventually propagate to your ear,

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which translates them into[br]electrical impulses

0:00:58.790,0:01:01.925
that your brain interprets as sound.

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The pitch of that sound depends on[br]the frequency of the compressions.

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A quickly vibrating string will cause[br]a lot of compressions close together,

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making a high-pitched sound,

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and a slow vibration [br]produces a low-pitched sound.

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Four things affect the frequency[br]of a vibrating string:

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the length, the tension,[br]the density and the thickness.

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Typical guitar strings [br]are all the same length,

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and have similar tension,[br]but vary in thickness and density.

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Thicker strings vibrate more slowly,[br]producing lower notes.

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Each time you pluck a string,

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you actually create [br]several standing waves.

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There's the first fundamental wave,[br]which determines the pitch of the note,

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but there are also waves[br]called overtones,

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whose frequencies [br]are multiples of the first one.

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All these standing waves combine[br]to form a complex wave with a rich sound.

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Changing the way you pluck the string[br]affects which overtones you get.

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If you pluck it near the middle,

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you get mainly the fundamental[br]and the odd multiple overtones,

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which have anti-nodes[br]in the middle of the string.

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If you pluck it near the bridge,[br]you get mainly even multiple overtones

0:02:14.358,0:02:16.410
and a twangier sound.

0:02:16.410,0:02:22.257
The familiar Western scale is based on[br]the overtone series of a vibrating string.

0:02:22.257,0:02:27.261
When we hear one note played with another[br]that has exactly twice its frequency,

0:02:27.261,0:02:29.195
its first overtone,

0:02:29.195,0:02:33.203
they sound so harmonious[br]that we assign them the same letter,

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and define the difference between them[br]as an octave.

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The rest of the scale [br]is squeezed into that octave

0:02:40.115,0:02:42.102
divided into twelve half steps[br]

0:02:42.102,0:02:48.039
whose frequency is each 2^(1/12)[br]higher than the one before.

0:02:48.039,0:02:51.290
That factor determines the fret spacing.

0:02:51.290,0:02:57.115
Each fret divides the string's[br]remaining length by 2^(1/12),

0:02:57.115,0:03:00.581
making the frequencies [br]increase by half steps.

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Fretless instruments, like violins,

0:03:02.601,0:03:06.926
make it easier to produce the infinite[br]frequencies between each note,

0:03:06.926,0:03:10.519
but add to the challenge [br]of playing intune.

0:03:10.519,0:03:12.581
The number of strings and their tuning

0:03:12.581,0:03:15.793
are custom tailored [br]to the chords we like to play

0:03:15.793,0:03:17.980
and the physiology of our hands.

0:03:17.980,0:03:20.863
Guitar shapes and materials can also vary,

0:03:20.863,0:03:24.527
and both change the nature [br]and sound of the vibrations.

0:03:24.527,0:03:27.206
Playing two or more [br]strings at the same time

0:03:27.206,0:03:32.205
allows you to create new wave patterns[br]like chords and other sound effects.

0:03:32.205,0:03:36.279
For example, when you play two notes[br]whose frequencies are close together,

0:03:36.279,0:03:41.605
they add together to create a sound wave[br]whose amplitude rises and falls,

0:03:41.605,0:03:46.500
producing a throbbing effect,[br]which guitarists call the beats.

0:03:46.500,0:03:49.506
And electric guitars give you [br]even more to play with.

0:03:49.506,0:03:51.692
The vibrations still start in the strings,

0:03:51.692,0:03:55.931
but then they're translated [br]into electrical signals by pickups

0:03:55.931,0:03:59.084
and transmitted to speakers [br]that create the sound waves.

0:03:59.084,0:04:00.909
Between the pickups and speakers,

0:04:00.909,0:04:04.675
it's possible to process [br]the wave in various ways,

0:04:04.675,0:04:11.758
to create effects like distortion,[br]overdrive, wah-wah, delay and flanger.

0:04:11.758,0:04:16.139
And lest you think that the physics [br]of music is only useful for entertainment,

0:04:16.139,0:04:18.059
consider this.

0:04:18.059,0:04:20.822
Some physicists think that everything[br]in the universe

0:04:20.822,0:04:26.892
is created by the harmonic series[br]of very tiny, very tense strings.

0:04:26.892,0:04:29.468
So might our entire reality

0:04:29.468,0:04:33.770
be the extended solo [br]of some cosmic Jimi Hendrix?

0:04:33.770,0:04:39.125
Clearly, there's a lot more to strings[br]than meets the ear.