Despite their detractors, pitch-correction tools and techniques have enjoyed widespread use in the studio, and for good reason. Used judiciously, pitch correction makes tracks sound sweeter and more harmonious. True, those characteristics may not be desirable for some styles of music. But for others, pitch correction is an indispensable technique that gives a production that extra bit of polish.
In this article, I'll offer practical, hands-on tips for getting the best results from pitch-correction software. I'll cite examples of how to use three of the most popular pitch-correction plug-ins: Antares Auto-Tune, Celemony Melodyne Plugin, and Waves Tune. The focus will not be on feature lists of each plug-in but on real-world uses to arrive at the best-sounding tracks. Because this is a master class, I'll skip most of the basics and assume that you already have some experience with at least one of the showcased plug-ins.
Space constraints don't permit a discussion of pitch transposition of polyphonic material or harmonization here. This article's emphasis will be on correcting the pitch of “off-key” monophonic tracks, specifically vocals. Much of what I will discuss can also be applied to other monophonic tracks, such as guitar melodies and bass lines.
Bursting at the Seams
I'll dive into plug-ins in a moment, but first a few pointers about DAW editing vis-à-vis pitch correction are in order. Before I apply pitch correction to a vocal track, I make sure any edits within the track have ultrasmooth transitions in order to reduce pitch-processing artifacts. This usually requires that any seam between adjoining audio regions occur at a zero crossover point for both regions. Failing to choose a zero crossover point results in instantaneous changes in level at the edit point, which can cause pitch-correction algorithms to produce pops and clicks — even in cases where the unprocessed edit point might not offend.
Additionally, edit points that consistently handle pitch-correction processing the most transparently are those at which both audio regions' waveforms are progressing toward the same polarity (that is, positive or negative excursion). What you don't want, for example, is for audio in the leading region to be heading into a negative waveform excursion at its zero crossover point, only to be whipsawed into a positive excursion after the trailing region's adjoining zero crossover point. Such a fast reversal in polarity often results in pops and clicks or warbly-sounding artifacts once pitch processing is applied to the track.
Where it is not possible to find an edit point at zero crossover points with smooth polarity transitions, applying a crossfade over the compromised edit seam will often gloss things over. Just make sure the crossfade is no longer than it needs to be. A crossfade extends the leading audio region farther along the timeline and the trailing region earlier along the timeline while crossfading between the two where their extensions overlap. Audio that fluctuates wildly in level or pitch, but which voices within the crossfade zone, can also cause pitch-correction artifacts. So listen carefully to any crossfades to see if they sound transparent after pitch correction is applied.
Quick and Not So Dirty
One of Auto-Tune's biggest strengths is that its Automatic mode can be used to correct pitch on the fly (that is, without having to first preload the audio into the plug-in for analysis). This lickety-split action is a godsend when you're pressed for time, such as when mixing demos for clients on a very thin budget.
Quick phrases that contain severely off-pitch notes may prompt you to use Automatic mode's faster Retune settings to attain sufficient pitch correction before the offending notes pass. However, such a heavy hand can also increase warbly- or phasey-sounding artifacts.
One solution is to chain two Auto-Tune plug-ins together in series to create a soft-knee effect. The first instantiation is set for a slow Retune time of roughly 50 to 90 ms in order to gently nudge the track's pitch closer but not all the way to where you want it to be. The second Auto-Tune instantiation is set for a faster Retune time of perhaps 20 to 30 ms, moving the pitch even closer to center. With this setup, neither plug-in has to work too hard, thereby (usually) reducing artifacts.
Whether you're working in Auto-Tune's Automatic mode or Graphical mode, applying pitch correction to a vocal track that has a heavy dose of tube distortion can cause pops and clicks. These artifacts can often be completely eliminated by setting the Tracking control to 1, its lowest setting. The Tracking control is accessed in Auto-Tune 5 by clicking on the Options button.
Auto-Tune offers a number of useful features for MIDI mavens. When a song includes one or more key changes, you might be tempted to choose a chromatic scale in Automatic mode to properly treat notes that don't belong to the key signature that starts off the song. But for more-exact pitch discrimination, try using Auto-Tune's Learn Scale From MIDI mode to select all the notes from both scales (and no others) for pitch-correction processing (see Fig. 1).
To do this, first create a new MIDI track in your DAW and assign your keyboard controller to its input. Send the MIDI track's output to Auto-Tune. For example, in MOTU Digital Performer (DP) assign the output to “Auto-Tune 5 (mono): name of vocal track: insert position.” Then click on Auto-Tune's Learn Scale From MIDI button. Doing so will automatically change the current scale type to chromatic and activate the plug-in's virtual keyboard.
Next, click on either the Octave As Played or Octave All button to make your subsequent note selections active only in the specific octave range you play them in or across all octaves, respectively. Then play on your MIDI keyboard controller all the notes that occur in your song's melody. The timing for note entry is not important, so take your time. If you enter a wrong note by mistake, click on the Learn Scale From MIDI button twice and start over, or simply activate the Keyboard Edit's Remove button and click on Auto-Tune's virtual keyboard on the notes you want to remove.
Once all of your melody's notes are entered, Auto-Tune should handle all of your key changes — unless, of course, some notes are sung more than 50 cents off-pitch and get pulled to a target pitch for another key used elsewhere in your song. In such a case, standard operating procedure in Auto-Tune is to enter Graphical mode and draw the target pitch for that note using the Line tool. (Waves Tune also offers a Line tool for graphic editing, which I'll discuss shortly.) By holding down the Option key (Mac) or Alt key (Windows) on your QWERTY keyboard while drawing, you can make Auto-Tune's Line tool draw a perfectly horizontal line on the pitch graph to keep the target pitch from fluctuating. Auto-Tune 5's new Snap To Note function goes one better, forcing the curve to be drawn to the nearest semitone.
MIDI-philes can accomplish the same result without ever entering Auto-Tune's Graphical mode. Simply click on the Target Notes Via MIDI button and play into your DAW the MIDI note that corresponds to your desired pitch. (You can also record it into a new MIDI track within your DAW.) Play the MIDI note immediately after the onset of the sung note and sustain it for the full duration of the note.
Mellow Dining with Plug-ins
In Melodyne Plugin, errant notes are moved to their pitch center simply by double-clicking with the Pitch tool on their Blobs (graphic representations of sung notes). The Pitch tool can also be used to drag an unintentionally nondiatonic note to the correct pitch belonging to the melody's scale. For this application, Melodyne Plugin's Scale Snap function is a real time-saver (see Figs. 2a and 2b).
After playing the offending note into Melodyne Plugin's analysis engine, select Scale Snap from the drop-down menu in the lower left corner of the plug-in's window. In the Note Ruler along the left edge of the window, click on the letter name that corresponds to the current key signature; Shift-clicking toggles the scale between major and minor keys having the same tonic note.
Now drag the off-key Blob to its desired pitch using the Pitch tool. As you drag the Blob up or down, it will snap to notes belonging to the scale you chose in the Note Ruler. However, any offset from exact pitch center that existed before dragging will remain after the Blob is dragged to the new note. If you want the Blob's pitch to be corrected fully, simply double-click on the Blob with the Pitch tool (after first dragging the Blob to its new note in Scale Snap mode).
If you don't own any pitch-correction software, your DAW probably has a pitch-shifting function that can be used to transpose isolated notes in a similar fashion (although the process will likely be tedious). For instance, I've used DP's Spectral Effects processing (see Fig. 3) to transpose pickup notes (fleeting notes sung before the downbeat of the first full bar of a phrase). Even great singers often sing these notes off-key by as much as a major third or more, and fixing each of these wild pitches can have a subtle yet noticeable impact on the overall performance.
If you use DP, make a time-range selection for the offending note. Be sure to select slightly more material than you think you'll need at both the start and end points of the time-range selection; you can always trim these sound-bite edges back afterward. Because Spectral Effects is a “constructive” process that creates an entirely new audio region whose edges cannot be extended after rendering, selecting a slightly larger region gives you more flexibility in placing transparent-sounding edit seams with any preceding and following audio regions.
Once your time-range selection is made, audition it by using the Option-Spacebar command and guesstimate how much you need to transpose the audio to place its pitch right on the money. Then call up DP's Spectral Effects command under the Audio menu and enter the required amount of pitch-shift in half steps and hundredths of a half step. The exact amount of pitch-shift needed will be a hit-and-miss determination best made by applying Spectral Effects processing, auditioning the result, and undoing and reapplying (with different pitch-shift amounts) as needed until it sounds right.
Catching a Vibe
Sometimes it's not a note's pitch center but an excessive amount of vibrato that causes a performance to sound off-pitch. Melodyne Plugin's Pitch Modulation tool is extremely effective in taming over-the-top vibrato, and using it is child's play.
After playing the offending portion of the performance into Melodyne Plugin, select the Pitch Modulation tool from the Pitch tool's drop-down menu. Then simply move the tool's cursor over the sound Blob that exhibits the excessive vibrato and drag downward with your mouse. The farther down you drag, the more the vibrato is reduced — to the point of complete elimination, if you want (see Web Clips 1 and 2).
Excessive vibrato can cause Waves Tune to graphically split one held note into multiple note segments having different pitches (see Fig. 4a). If this occurs, set a high Note Tolerance (in the plug-in's Segmentation controls section) and rescan the offending phrase. The high Note Tolerance setting should preclude segmentation into multiple pitches, while also creating a tighter pitch-correction curve that doesn't swing over such a wide pitch range (see Fig. 4b).
With Tune's audio analysis tweaked, now it's time to tame that unruly vibrato. Turn on Tune's Natural Vibrato function (located in the Vibrato controls section in the plug-in's lower right corner) and reduce the Amount value to decrease the track's vibrato effect. If the vibrato becomes excessive only at the end of a sustained note, you can increase the Vibrato Attack time so that your programmed vibrato reduction kicks in only during the problematic portion of the note. To completely flatten the vibrato effect so that there is no pitch fluctuation, you may need to lower Tune's Speed control to 0.
Of course, you can also reign in wildly fluctuating pitch by drawing a flat (constant) pitch target with Tune's Line tool. Click on your desired pitch with the Line tool in Tune's Pitch Edit Area and draw a line from the start to the finish of the offending phrase, double-clicking at the end of the phrase. Use of the Line tool will automatically change Tune's Speed, Note Transition, and Ratio values, so be sure to readjust them to taste.
Stick to Me Like Glue
Looking at Fig. 4b again, check out the two short, additional segments at the onset of the held note. These are unwanted and unnecessary note segments that only complicate editing in Tune. Clicking on them with Tune's Glue tool will join them to the following long segment, making one segment out of all three.
Where note segments are of different pitches, you can join them together and simultaneously tune them all to one pitch. Simply select all the segments and then click on the one that has the desired pitch with Tune's Glue tool.
The Right Tool
Your needs will dictate which pitch-correction tool is best for the job at hand. Auto-Tune's Automatic mode makes it the easiest and quickest pitch-correction plug-in to use. Both Auto-Tune and Tune can set pitch targets by inputting MIDI notes. Tune also offers microtonal tuning and ReWire-style control over the host's basic transport functions. But unlike Auto-Tune and Melodyne Plugin, Tune doesn't support tempo changes and will introduce pops and clicks when confronted with them. Melodyne Plugin is the most complicated but by far the most powerful plug-in of the lot; in addition to pitch correction, it can do things that Tune and Auto-Tune can only dream of, such as intelligent harmonization, timing quantization, and time compression and expansion.
As with other types of production tools, sparing usage and a deft hand are key to getting the most natural-sounding results. Use your ears and don't overdo it. Then enjoy the sweet sound of success.
EM contributing editor Michael Cooper is the owner of Michael Cooper Recording in Sisters, Oregon. Visit him atwww.myspace.com/michaelcooperrecording.