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Gripped with vengeful passion,

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The Queen of the Night 
tears across the stage.

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She begins to sing her titular aria,

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one of the most famous sections 
from Mozart’s beloved opera,

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"The Magic Flute."

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The orchestra fills the hall with music,

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but the queen’s voice soars above 
the instruments.

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Its melody rings out 
across thousands of patrons,

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reaching seats 40 meters away—

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all without any assistance 
from a microphone.

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How is it possible that this single voice
can be heard so clearly,

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above the strains 
of dozens of instruments?

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The answer lies in the physics 
of the human voice,

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and the carefully honed technique 
of an expert opera singer.

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All the music in this opera house 
originates from the vibrations

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created by instruments—

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whether it’s the strings of a violin 
or the vocal folds of a performer.

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These vibrations send waves into the air, 
which our brains interpret as sound.

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The frequency of these vibrations––

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specifically, the number 
of waves per second––

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is how our brains determine 
the pitch of a single note.

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But in fact, every note we hear

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is actually a combination 
of multiple vibrations.

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Imagine a guitar string vibrating 
at its lowest frequency.

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This is called the fundamental,

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and this low pitch is what our ears 
mostly use to identify a note.

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But this lowest vibration triggers 
additional frequencies called overtones,

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which layer on top of the fundamental.

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These overtones break down 
into specific frequencies

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called harmonics, or partials—

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and manipulating them 
is how opera singers work their magic.

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Every note has a set of frequencies 
that comprise its harmonic series.

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The first partial vibrates 
at twice the frequency of the fundamental.

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The next partial is three times 
the fundamental’s frequency, and so on.

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Virtually all acoustic instruments 
produce harmonic series,

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but each instrument’s shape and material
changes the balance of its harmonics.

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For example, a flute emphasizes 
the first few partials,

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but in a clarinet’s lowest register,

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the odd-numbered partials 
resonate most strongly.

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The strength of various partials

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is part of what gives each instrument
its unique sonic signature.

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It also affects an instrument’s ability 
to stand out in a crowd,

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because our ears are more strongly 
attuned to some frequencies than others.

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This is the key to an opera singer’s 
power of projection.

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An operatic soprano—

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the highest of the four standard 
voice parts—

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can produce notes 
with fundamental frequencies

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ranging from 250 to 1,500 vibrations 
per second.

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Human ears are most sensitive 
to frequencies

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between 2,000 and 5,000 
vibrations per second.

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So if the singer can bring out 
the partials in this range,

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she can target a sensory sweet spot 
where she’s most likely to be heard.

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Higher partials are also advantageous

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because there’s less competition 
from the orchestra,

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whose overtones are weaker 
at those frequencies.

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The result of emphasizing 
these partials

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is a distinctive ringing timbre 
called a singer’s squillo.

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Opera singers work for decades 
to create their squillo.

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They can produce higher frequencies

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by modifying the shape and tension 
in their vocal folds and vocal tract.

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And by shifting the position 
of their tongues and lips,

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they accentuate some overtones 
while dampening others.

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Singers also increase their range 
of partials with vibrato—

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a musical effect in which a note 
slightly oscillates in pitch.

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This creates a fuller sound 
that rings out

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over the instruments’ 
comparatively narrow vibratos.

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Once they have the right partials,

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they employ other techniques 
to boost their volume.

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Singers expand their lung capacity 
and perfect their posture

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for consistent, controlled airflow.

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The concert hall helps as well,

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with rigid surfaces that reflect 
sound waves towards the audience.

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All singers take advantage 
of these techniques,

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but different vocal signatures 
demand different physical preparation.

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A Wagnerian singer needs 
to build up stamina

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to power through the composer’s 
four-hour epics.

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While bel canto singers require 
versatile vocal folds

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to vault through acrobatic arias.

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Biology also sets some limits—

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not every technique is feasible 
for every set of muscles,

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and voices change as singers age.

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But whether in an opera hall 
or a shower stall,

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these techniques can turn 
un-amplified voices

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into thundering musical masterpieces.