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Gripped with vengeful passion,

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The Queen of the Night tears [br]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[br]Mozart’s beloved opera, 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 [br]the instruments.

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Its melody rings out across thousands [br]of patrons,

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reaching seats 40 meters away— all [br]without any assistance from a microphone.

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

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above the strains of dozens [br]of instruments?

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The answer lies in the physics of the [br]human voice,

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and the carefully honed technique [br]of an expert opera singer.

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All the music in this opera house [br]originates from the vibrations

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created by instruments—

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

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

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The frequency of these vibrations––

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specifically, the number of [br]waves per second––

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

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But in fact, every note we hear

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is actually a combination [br]of multiple vibrations.

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Imagine a guitar string vibrating at its[br]lowest frequency.

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This is called the fundamental,

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

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But this lowest vibration triggers [br]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 [br]frequencies called harmonics, or partials–

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and manipulating them is how [br]opera singers work their magic.

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

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The first partial vibrates at twice the [br]frequency of the fundamental.

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

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Virtually all acoustic instruments [br]produce harmonic series,

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

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For example, a flute emphasizes the [br]first few partials,

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but in a clarinet’s lowest register,

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the odd-numbered partials [br]resonate most strongly.

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The strength of various partials

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

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

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

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

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An operatic soprano— the highest [br]of the four standard voice parts—

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can produce notes with fundamental[br]frequencies

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ranging from 250 to 1,500 vibrations [br]per second.

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Human ears are most sensitive to [br]frequencies

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between 2,000 and 5,000 [br]vibrations per second.

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

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she can target a sensory sweet spot [br]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 [br]from the orchestra,

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whose overtones are weaker at [br]those frequencies.

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The result of emphasizing these [br]partials

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is a distinctive ringing timbre [br]called a singer’s squillo.

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Opera singers work for decades to [br]create their squillo.

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They can produce higher frequencies

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

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And by shifting the position of their [br]tongues and lips,

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they accentuate some overtones [br]while dampening others.

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Singers also increase their range of [br]partials with vibrato––

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a musical effect in which a note slightly [br]oscillates in pitch.

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This creates a fuller sound that rings [br]out

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over the instruments’ comparatively[br]narrow vibratos.

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Once they have the right partials,

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they employ other techniques to [br]boost their volume.

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Singers expand their lung capacity and[br]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 [br]waves towards the audience.

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All singers take advantage of these [br]techniques,

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but different vocal signatures demand [br]different physical preparation.

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A Wagnerian singer needs to build up [br]stamina

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

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While bel canto singers require versatile [br]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[br]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 [br]shower stall,

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these techniques can turn unamplified [br]voices

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into thundering musical masterpieces.