Pitch Perfect

  • By David Levin
  • Posted 04.01.09
  • NOVA scienceNOW

Learning to sing like Aretha Franklin isn't something you can do overnight. But over the past decade, recording studios have been fudging things a bit with software called Auto-Tune, which enables them to change the pitch of sour notes. In this interactive, find out how it works and see if it can make even hopeless singers, like some on the NOVA staff, sound tolerable.

Launch Interactive

Learn what pitch is, then listen in as Auto-Tune corrects the bad pitch of several NOVA staffers.


Pitch Perfect


DAVID LEVIN: Before we start, let's take a step back to the basics. To understand what Auto-Tune software can do for, well, untrained singers, you need to understand how the sound of a musical note is made.

It all starts with something vibrating – It could be the metal of a bell,

[bell rings]

or the skin of a drum,

[drum sound]

or a string on a guitar.

[guitar sound]

ANDY HILDEBRAND: With the human voice, it's the vocal cords vibrating over and over.

DAVID LEVIN: That's Andy Hildebrand – He invented the Auto-tune software.

ANDY HILDEBRAND: When you hear an "A", you're hearing 440 vibrations per second.

[Singer singing A440]

DAVID LEVIN: A "B" is about 492 vibrations per second,

[singer singing B492]

DAVID LEVIN: And a "C" is around 587.

[Singer singing C587]

ANDY HILDEBRAND: That's about right.

DAVID LEVIN: So the faster the vibration, the higher the pitch. Simple enough. But pitch isn't the only thing that determines the way a musical note sounds. The shape of an instrument plays a role, too. That's why a bass…

[acoustic bass note]

…sounds different from a banjo,

[banjo note]

…even when they're playing the exact same note.

[acoustic bass and banjo together]

In humans, the size and contours of the spaces inside our heads and throats color the way our voices sound.

ANDY HILDEBRAND: The human voice resonates based on the shape of the throat, the nasal passages, and the speaker's mouth.

DAVID LEVIN: So no matter what note someone is singing, their voice is still unique and recognizable. Jonathan here…


DAVID LEVIN: …will always sound like Jonathan, and Cass…

CASS: Hey there.

DAVID LEVIN: …will always sound like Cass. Even if they sing at the same time.

[Jonathan and Cass singing together]

DAVID LEVIN: But what if they want to improve their singing voices? What can Auto-Tune do for them?



DAVID LEVIN: The first thing that Auto-Tune does is figure out the pitch of a note that is sung or played into the computer. It's recorded as a red line on this grid.

An "A", for example, would fall on this line. A B-flat would fall on the line above it, and a G-sharp would be on the line below. But singing those exact notes is hard, especially if you don't have any training.


DAVID LEVIN: So let's say you're trying to hit an "A", and you're a little off.

[bad singer with warbly voice]

Okay, a lot off. Your pitch—that's the red line—wavers back and forth around the right note. Auto-tune can tell which parts of the sound are higher or lower than they should be, and it's able to nudge them back into tune.

[singer's voice corrected in Auto-Tune]

It can even help out if you sing the wrong note entirely. For example, if you hit an "A" when you should have been singing a "high G"—Auto-Tune can bump your voice up to the right note.

Here's a slightly better singer. Those red lines are the original pitch of her notes. The blue blocks show where it's been corrected.

[singer's voice in Auto-Tune]

It takes some serious mathematical processing for Auto-tune to make these corrections sound natural, though. If it only altered the pitch of someone's voice, it might sound like this:

[chipmunk voice]

ANDY HILDEBRAND: You get a chipmunk effect. It's not their voice anymore.

DAVID LEVIN: So Andy Hildebrand designed Auto-tune to avoid this problem. Rather than just shifting a singer's pitch, the software also models the shape of the singer's mouth and throat.

ANDY HILDEBRAND: So we, like, cut their neck off, listen to their vocal cords, change the pitch, and then glue their head back on. (Laughs) And we do that mathematically in real time. And that's how we can change the pitch of a singer without creating the chipmunk effect.

DAVID LEVIN: Auto-Tune can't make dramatic changes in pitch—say, going from "middle C" to a "high A" without sounding mechanical and robotic. But some musicians and record producers actually seek out these effects. They're using Auto-Tune to make new sounds.


DAVID LEVIN: Auto-Tune creates an unnatural, robotic effect when its settings are pushed to the extremes. But that can sometimes be a creative tool. Musicians from Cher to T-Pain are using it on top-40 albums.

By shifting a note too high in Auto-Tune, you can give it a thin, ghostly effect:

[singer's voice processed into high, ghostly sound]

DAVID LEVIN: And by making rapid adjustments in a singer's pitch, you can make the voice sound robotic. You might recognize this one.

[Singer's voice processed into robotic sound]

DAVID LEVIN: Andy Hildebrand never meant for Auto-Tune to be used this way. But right now, Auto-Tunes signature effects are all over the radio.

AH: This effect is found in every music genre from Dollywood, to Reggae, to Country, Pop, Hip-Hop… everywhere.

DAVID LEVIN: That's great for top-40. But what about the NOVA staff? Can Auto-Tune help our amateur vocalists sound like the pros?



[Aretha Franklin singing My Country 'Tis Of Thee" at inauguration of President Obama]


[NOVA staff singing "My Country 'Tis Of Thee" out of tune]


[NOVA staff singing "My Country 'Tis Of Thee"; Auto-Tuned version]


ANDY HILDEBRAND: Generally, a bad-sounding singer using Auto-tune is going to sound like a bad-sounding singer who happens to be in tune. We can't fix that. If they've got a poor tone quality, or a poor style, or don't support their diaphragm and get an even volume, we can't fix those things. (laughs)



(guitar, banjo)
© istockphoto/Don Bayley
© istockphoto/Diane Diederich
© istockphoto/Alex Kalmbach
© istockphoto/Jake Holmes
(Harold "Andy" Hildebrand)
Courtesy Harold Hildebrand
(Jonathan Loewald; Cass Sapir; Cass Sapir and Jonathan Loewald; David Levin; Darcy Forlenza, David Levin, and Jonathan Loewald)
© WGBH Educational Foundation
© AP Images/Jason DeCrow
© AP Images/Mitchell Zachs
(Aretha Franklin)
© AP Images/Ron Edmonds

Related Links

  • Auto-Tune

    Can't carry a tune? Andy Hildebrand's pitch-correction software can help you sing like a star.

  • Auto-Tune: Expert Q&A

    Andy Hildebrand answers questions about Auto-Tune, the implications of its use among professional musicians, and more.


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