The latest pitch manipulation tools sound more natural-and offer more creative possibilities than ever before.
Technology Pitches In
Auto-Tune's automatic mode lets users chose which notes will receive correcting and which will be ignored.
Auto-tune's graphic mode lets users "draw" in pitch correction on a note-by-note basis.
Antares Harmony Engine can create four-part harmonies.
Celmony's Melodyne displays audio on a sequencer-like grid. Each note can be moved in pitch or time.
BIAS's PitchCraft includes both pitch correction and transposition.
Hardware Pitches In
Thanks tp fast computers and the realities of the modern studio, software dominates today's pitch-correction/shifting scene. But there are still standalone hardware devices available. Antares Vocal Producer rack unit combines the effects included in its various pitch-manipulation programs, as compression, mic modeling, and other audio processing. Digitech makes several rack and floor effects in its Vocalist series that do pitch correction and harmonization and can accept MIDI input. TC-Helicon's rack mounted VoiceWorks Plus and Voice Pro, plus its floor-based Voice Live and others offer various levels of processing, from basic pitch correction to intense voice and pitch manipulation. Instrumentalists might want to check out the Boss PS-5, which offers chromatic and diatonic pitch shifting and harmony in a compact pedal. Then there's Eventide, the company that coined the term Harmonizer back in the last century; The Eclipse, which sits in the middle of its range, cost wise, offers harmonization and "Micro" pitch shifting.
Whether you think of it as a Godsend or as a crutch that's taken the soul out of music, pitch correction is here to stay. Products like Antares Tech's Auto-Tune (which has become so ubiquitous that "Auto-Tuning” has the generic connotation that "Xeroxing” used to have back in the day) have been employed on countless records, sometimes unobtrusively bringing tracks into pitch, and sometimes being used so blatantly that you wonder if the singer ever hit a single note.
But there's more to pitch correction and manipulation software than simply tracking notes and automatically quantizing them to a specific frequency. The latest software also offers a lot of creative potential, from the automatic generation of harmonies to the ability to alter melodies after they've been recorded and convert audio to MIDI. Recent products like Antares Auto-Tune Vocal Studio (a suite that includes a harmony generator along with the latest version of Auto-Tune, which is also available as part of the company's hardware Vocal Producer), Celemony's Melodyne Studio (which lets you manipulate audio with the same control as MIDI), BIAS Inc.'s PitchCraft, and TC Electronic's Intonator (which is available as a Powercore plug-in and as a hardware unit), and Waves' Tune, can help you develop complex vocal and instrumental tracks. Even sequencers are getting into the act; Apple's Logic Pro comes with a built-in pitch correction plug-in, while and Cakewalk's SONAR comes with Roland's V-Vocal plug-in.
How Pitch Correction Works
Modern pitch correction uses complex software number-crunching to analyze the frequency of an incoming audio signal, compare it to a "target” frequency, and then adjust the pitch up or down to meet this target. If you're familiar with the way a drum machine or sequencer's "quantize" feature works—where notes are moved so that they trigger exactly on a specified beat—you have the basic idea. In fact, pitch correction is a form of quantization.
The most important feature in any pitch-shifting device—whether it's being used to correct pitch or to generate harmonies— is its ability to accurately track the pitch coming in. Bad tracking can result in two problems: wrong notes and weird, robotic sounds. Fortunately, the latest algorithms are way more accurate than the products of a few years ago. They are better able to handle complex material and variations in timbre, which helps for accurate pitch correction and good-sounding harmonies.
But as with tempo, completely "accuracy" is not always a good thing. As an overly quantized groove might sound mechanical, so too roughly pitch-corrected a performance can sound robotic. In extreme cases, it can lend a human vocal the sound of a Vocoder or voice synth, as in Daft Punk's "One More Time." Producers have pitch-corrected without shame for years, and there's even a web listing of some of the more obvious examples (check out hometracked.com/2008/02/05/auto-tune-abuse-in-pop-music-10-examples). But what if you don't want people to know you're tweaking pitch?
Fortunately, the better pitch-correcting products let you specify how close to perfect you want the pitch to be. But because pitch can be more complex than tempo, there are other factors to consider.
One "key" setting (sorry, the pun was too obvious to ignore) is retune speed, which determines how long a note will play before the pitch correction kicks in. Fast times yield the kind of "stair step" effect that listeners can hear as "obvious" pitch correction, whereas longer attack times let the note seem to bend up or down to the pitch more naturally. Auto-Tune has a switch that tells the software to ignore vibrato, allowing that important expressive tool to remain in tact, and a humanize function that lets you set the a fast retune speed (to keep short notes accurate) while allowing a sustaining note to retain its natural pitch fluctuation.
But what if other instruments in a song are not tuned to a reference frequency of A=440 Hz (which is the standard in most places)? Tuning software can be adjusted to use other reference frequencies as a baseline, and also so that the target note is a given number of cents (100 cents equals one semitone) sharp or flat of a given note's normal pitch. This is important if, for example, you've recorded a track to a guitar that was tuned by ear, which may be in tune with itself but not with the rest of the modern world.
Another important element in setting up tuning software is to define just which notes need to be corrected, and to what target notes. Simply setting the software to a chromatic scale may not yield ideal results. If, for example, the singer is about 50 cents flat of C, the software might think he's going for B-flat and tune accordingly— or worse, jump between the two notes. Most programs let you define a scale to which all corrected note will conform. Depending on the pitch correcting device or software you're using, there are three options: choosing a diatonic or other scale among a set of prese; manually entering the notes to include in your scale; and by playing the scale in via MIDI. Auto-tune, for example, can even track pitch to a scale played back in real time, so you can literally play the melody and have the recorded performance conform to it. How natural this sounds, however, has a lot to do with how far the software is shifting the pitch. The closer the shift, the more natural the results.
Automatic pitch correction works pretty well about 75 percent of the time, but where you need to be extra careful about nuance, a graphical editor may be more effective. This lets you "draw" your pitch correction in for each note. It can be painstaking work, but can also yield very natural results.
Celemony's Melodyne takes the graphic approach to the extreme. In addition to tracking the pitch, it can display incoming audio as in both a sequencer-like piano roll and as musical notaiton (see figure X). It can be used to correct pitch for an entire performance, or only for selected notes, and the level of correction can be set to be relatively loose or 100 percent accurate.
But in addition to correcting notes, Melodyne lets you edit an audio performance in virtually the same way you would move events in a MIDI a sequencer. for example, you can grab a single note and alter its pitch or time position. Or you can copy one note or an entrie track and use it to build a unique harmony, create counterpoint, and more.
Melodyne can also output a standard MIDI file based on the audio it receives. So, for example, you can import a guitar solo, edit its timing, tweak its pitch, and then export a MIDI file that follows the track. From there, you can use the MIDI track to trigger, say, a string library or horn part.
What's the Har(mony)?
Creative uses for pitch-manipulation gear might be especially appealing to songwriters working on demos, because these tools let you try out a lot of ideas without having to re-sing a million parts. Plus, automatical harmonies can cover rages outside of your own. Even if you plan to replace these parts with real singers later, being able to hear and expirment with multiple parts is very useful.
However, if you're using a computer, this can be processor intensive work: you may want to freeze or disable any unnecessary plug-ins and tracks while working out the parts. Antares' Harmony Engine (a separate program from Auto-Tune, but part of the company's AVOX suite, which also includes formant shifters) BIAS's PitchCraft, and TC's Intonator can all generate automatic harmonies, while Melodyne lets you create them through copy and drag editing.
Pitch transposers/harmonizers that include formant shifting usually deliver more natural sound than devices that only shift pitch. In lay terms, the formant refers to the timbral qualites that give a voice its male or female character.
Ultimately, the success you have with pitch manipulation depends on how much time you're willing to spend tweaking. Simply throwing some pitch correction on a track will probably yield accurate pitches but unnatural sound. Experimentation (and your ears) will tell you when to turn the effect on (and when to leave it off), how to tweak its response time to match your incoming signal, and how to set the scale to track and accurately adjust pitch.
Sure, these programs may be seen as a crutch, and maybe they are occasionally abused—people in the industry still joke about the obvious pitch shifting known as the "Cher" effect. But pitch shifting can also create unique sounds, and, more important, save a great expressive performance that happen to have a bum note or two.