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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.