Pitch Correction

   By Emilie L   Categories: Mixing Techniques

Picture from Flickr user Audiotecna Musica

The best solution to an out-of-tune note is to record a new performance: an in-tune performance. Allow me to reiterate: the best way to get a track in tune is to record a performer who is in tune. Alas, recording sessions don’t always go smoothly. Performers might connect with their fans through features other than pitch accuracy. Production schedules and funding can conspire to put us in a bind, pitch-wise. And so we find ourselves needing a pitch shifter to fix any annoyingly out-of-tune notes that can’t be retracked.

Many a session goes like this: It’s 4:19 a.m. It’s the seventeenth take of the song. It’s a great take. Then on the last repeat of the last chorus, the singer—understandably tired from singing for so long—drifts flat on a key word. And now they are too tired to hit it. What to do?

First, we should listen back to old takes to see if we can edit in an in-tune replacement for that phrase or that word that is still musically compelling and consistent with the rest of the performance. Otherwise, we pitch-shift the problem.

In the old days of multitrack production (and you are encouraged to try this manual approach), the sour note was sampled. Using a pitch shifter, it was then manually tuned by ear, based on your musical judgment. It was raised or lowered to taste. Then, the sampled and pitch-shifted note was re-recorded and edited back onto the multitrack. With the problematic note shifted to pitch perfection, no one was the wiser.

Alternatively, and more frequently, we reach for pitch correction hardware or software. When it detects the sharp or a flat note, it shifts the pitch automatically by the amount necessary to restore tuning. We must listen acutely, watching the whole pitch-correction process and listening for anomalies that make the performance sound unnatural or disappointing.

First, specify the pitch center of the recording. If the whole band is tuned to A444, but the pitch-shifting processor is pulling everything to A440, you’ll never get the track in tune. In this way, we determine what counts as in tune.

Second, determine the key and scale that identifies the acceptable notes for the performance.

Third, spend some time adjusting the reaction time of the pitch-correction tool. This is essential if you want the pitch-corrected performance to sound convincing, natural, believable. We discuss deliberately unnatural pitch-shifting strategies later in this chapter. For pitch correction that casual listeners won’t notice as pitch-corrected, you need to allow a musical amount of missed, bent, or otherwise imprecise pitches through. It takes a light touch, sharp listening skills, and sound musical judgment to do it well. Too slow, and there will be too much that is out of tune in your tune. Too fast, and each note of the performance snaps unnaturally to the corrected pitch, making the performer sound crude or clumsy and creating a melodic contour that doesn’t support the emotional intent of the melody.

Finally, pay attention to the formant. Different pitch-correction tools offer different approaches, but you generally have controls that identify the type of track to be pitch-shifted and that specify the amount of formant manipulation to be tolerated.

Pitch correction is simple in concept, but you must listen carefully. Practice with each make and model of pitch shifter you use. Some are better than others, generally. But some are better than others for certain situations. Some are designed for vocals, and others might work well on electric bass. It takes time to learn how to coax a convincing performance out of the algorithm. You’ll need to practice with each plug-in.

As you develop facility with the parameters and figure out how to make it sound good, remain aware of pitch shifting’s limitations.

First, do not forget that it is the job of the mix engineer to choose when the pitch-shifted track offers any improvement to the recording versus when the original performed pitch is to remain. There is a strong temptation to “perfect” each and every track in a multitrack project. And if you—the mix engineer— aren’t the one tempted to do this, the performers will be. Don’t be surprised to get a tap on your shoulder from some of the other players while you are tuning the vocal; they are going to want a little bit of that on their sax solo, their synth line, their bass part, and so on. Seeing pitch shifting in action plays on the confidence of a performer. If a meter displays pitch errors, a player is going to want to fix it and make it error-free—make it “perfect.”

But “perfect” here is highly subjective. A track deemed perfect by pitch correction software may lack musical expressiveness and might be riddled with artifacts of the pitch-shifting process. Listen closely and stay critical. And don’t be afraid to reject the pitch-corrected version. There is everything from slightly, vaguely mistuned, to very clearly out-of-tune performances throughout the history of music. Tuning a track doesn’t always serve the art. Perfection is its own aesthetic, not suitable for all productions. When you don’t necessarily need perfection, don’t chase it.

As recording engineers, we are used to making the trade-off between aesthetic beauty versus objective correctness when they are in conflict. As mix engineers, we know the most musical use of our studio isn’t always the most technically correct. The members of the band don’t have this experience or this context. You must help them hear the track, without looking at the pitch-correction display, and decide when and—more importantly—when to use the correction effect.

Then there are the deliberate manipulations of pitch by the performer. Vibrato is an obvious example of the musical detuning of an instrument on purpose. And, if every note of a blues guitar solo were pitch-shifted into perfection, string bends unbent so that the pitch never strayed, how blue would those blues be? There is a lot to be said for a musical amount of “out-of-tune-ness.” Remove all the bends and misses, and we risk removing a lot of emotion from the performance.

Finally, there are limits. Producers should not expect to create an opera singer out of a folk singer, or a pitch-perfect pop star out of a wobbly, wandering wannabe. There is no replacement for actual musical ability. If the bass player can’t play a fretless in tune, don’t let them play a fretless in your tune. If the violin player can’t control his or her intonation, don’t let him or her play on your session. Don’t expect to rescue poor musicianship with automatic pitch correction. Use it to add to a stellar performance, not to create one. Musical sense and good judgment must motivate everything that is done in the recording studio. People generally want to hear the music, not the effects rack.

Excerpt from Mix Smart: Pro Audio Tips for your Multitrack Mix by Alex Case © 2011 Taylor & Francis Group. All Rights Reserved.

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