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Hendrix, Cobain and Page.

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They can all shred,

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but how exactly do the iconic 
contraptions in their hands

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produce notes, rhythm, melody and music.

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When you pluck a guitar string, you create
a vibration called a standing wave.

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Some points on the string, called nodes,
don't move at all,

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while other points, anti-nodes, 
oscillate back and forth.

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

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where the thin and flexible wood vibrates,

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jostling the surrounding air molecules
together and apart.

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These sequential compressions
create sound waves,

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and the ones inside the guitar
mostly escape through the hole.

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They eventually propagate to your ear,

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which translates them into
electrical impulses

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that your brain interprets as sound.

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The pitch of that sound depends on
the frequency of the compressions.

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

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making a high-pitched sound,

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and a slow vibration 
produces a low-pitched sound.

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Four things affect the frequency
of a vibrating string:

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the length, the tension,
the density and the thickness.

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Typical guitar strings 
are all the same length,

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and have similar tension,
but vary in thickness and density.

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Thicker strings vibrate more slowly,
producing lower notes.

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Each time you pluck a string,

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you actually create 
several standing waves.

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

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but there are also waves
called overtones,

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whose frequencies 
are multiples of the first one.

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

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Changing the way you pluck the string
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
and the odd multiple overtones,

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which have anti-nodes
in the middle of the string.

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

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and a twangier sound.

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The familiar Western scale is based on
the overtone series of a vibrating string.

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When we hear one note played with another
that has exactly twice its frequency,

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its first overtone,

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they sound so harmonious
that we assign them the same letter,

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and define the difference between them
as an octave.

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The rest of the scale 
is squeezed into that octave

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divided into twelve half steps


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whose frequency is each 2^(1/12)
higher than the one before.

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That factor determines the fret spacing.

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Each fret divides the string's
remaining length by 2^(1/12),

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making the frequencies 
increase by half steps.

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Fretless instruments, like violins,

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make it easier to produce the infinite
frequencies between each note,

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but add to the challenge 
of playing intune.

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The number of strings and their tuning

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are custom tailored 
to the chords we like to play

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and the physiology of our hands.

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Guitar shapes and materials can also vary,

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and both change the nature 
and sound of the vibrations.

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Playing two or more 
strings at the same time

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allows you to create new wave patterns
like chords and other sound effects.

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For example, when you play two notes
whose frequencies are close together,

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they add together to create a sound wave
whose amplitude rises and falls,

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producing a throbbing effect,
which guitarists call the beats.

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And electric guitars give you 
even more to play with.

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The vibrations still start in the strings,

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but then they're translated 
into electrical signals by pickups

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and transmitted to speakers 
that create the sound waves.

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Between the pickups and speakers,

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it's possible to process 
the wave in various ways,

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to create effects like distortion,
overdrive, wah-wah, delay and flanger.

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And lest you think that the physics 
of music is only useful for entertainment,

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consider this.

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Some physicists think that everything
in the universe

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is created by the harmonic series
of very tiny, very tense strings.

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So might our entire reality

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be the extended solo 
of some cosmic Jimi Hendrix?

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Clearly, there's a lot more to strings
than meets the ear.