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Master Class: Pitch Shifting in Pro Tools 8

June 1, 2009
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FIG. 1: The Elastic Audio plug-in button shows the name of the current plug-in, and the green light indicates that it is processing in real time. Command+Control-click (Control+Start-click on Windows) on the button to toggle between real-time and rendered processing.

FIG. 1: The Elastic Audio plug-in button shows the name of the current plug-in, and the green light indicates that it is processing in real time. Command+Control-click (Control+Start-click on Windows) on the button to toggle between real-time and rendered processing.

Digidesign introduced Elastic Audio in Pro Tools 7.4, offering powerful and flexible time correction within its industry-leading DAW. In Pro Tools 8, Elastic Audio sprouts a new ability to change the pitch of an audio region. Transposing a loop or tuning a vocal is just a few clicks away.

Don't put away your Melodyne just yet, however. Elastic Audio has no intelligent algorithm for determining pitch — there's no auto to this tuning. You can change a region's pitch by as much as two octaves in either direction in increments of a cent, but it's up to you to decide how much tuning is required. Furthermore, pitch changes are applied only to entire audio regions, so to change the pitch of a syllable you must first separate that syllable from the rest of the word.

Still, even as we wait and hope for the wizard to grant Elastic Audio a brain for tuning, we can get a lot of creative and corrective mileage out of its existing capabilities. In this “Master Class,” I'll share some techniques I use to make quick work of pitch manipulation in Pro Tools 8.

Elasticity

As with time correction, Elastic Audio pitch correction requires first that the track in question be declared an Elastic Audio track. Of the four available Elastic Audio plug-ins, only Polyphonic and Rhythmic allow pitch manipulation independent of time manipulation. Varispeed, of course, ties the two together, but it's counterintuitive that Monophonic doesn't work. If you have X-Form installed, it can be used for pitch manipulation, but not in real time. Given a fast processor, that may not be a problem as the rendering of a short phrase takes only a few seconds. If the delay is a problem, you can always work in real time with the Polyphonic or Rhythmic plug-in and then change the track to X-Form when you have it tuned. Polyphonic and Rhythmic can both operate in either real-time or rendered mode, and you can toggle that behavior by Command+Control-clicking (Control+Start-clicking on Windows) on the Elastic Audio plug-in button (see Fig. 1).

Whether Polyphonic or Rhythmic is best for a particular source is something only your ears can judge; no description I could offer would be a worthy substitute. X-Form, however, is better than either under almost any circumstance. You can set a default real-time Elastic Audio plug-in in Pro Tools' Preferences under Processing (see Fig. 2). Unfortunately, no third-party algorithms can be assigned for use by Elastic Audio. Given that the TCE Trim tool can use third-party plug-ins, I hope that Elastic Audio will eventually follow suit.

FIG. 2: Elastic Audio preferences let you choose which of the real-time plug-ins will be the default for new Elastic Audio–enabled tracks. This preference is linked to the plug-in chosen for preview in a browser.

FIG. 2: Elastic Audio preferences let you choose which of the real-time plug-ins will be the default for new Elastic Audio–enabled tracks. This preference is linked to the plug-in chosen for preview in a browser.

When using Elastic Audio for time correction, it's standard to make the track tick-based, but this may not be the best course for pitch correction. If you make the track tick-based, then Elastic Audio will automatically adjust to tempo changes, but you may not want your precisely edited and tuned lead vocal to do that. If not, make the track sample-based to preserve its timing regardless of tempo tweaks. For pitch-shifting loops, tick-based is still probably best.

Two caveats related to Elastic Audio pitch manipulation might affect your workflow when comping tracks. First, in Pro Tools HD you cannot use Elastic Audio on tracks with explicitly assigned voices. Elastic Audio tracks must use dynamic voice allocation. (This does not affect LE or M-Powered as they always use dynamic voice allocation.) Second, although region groups can include pitch-shifted regions and you can crossfade pitch-shifted regions, you cannot group crossfaded regions on an Elastic Audio-enabled track. Instead of grouping edited regions on a comp track, create a duplicate playlist and consolidate them. You can go back to the unconsolidated playlist to make changes if necessary; it's only one step more complex than grouping and ungrouping the regions.

Care in Carving

Because tuning is a region property, the first step is to separate the parts that need tuning. To change individual notes of a bass loop or any other part with clearly defined attacks, try using Tab to Transient to move the cursor from note to note. To toggle Tab to Transient on and off, press Command+Option+Tab (Control+Alt+Tab). Turn Commands Keyboard Focus on by pressing Command+Option+1 (Control+Alt+1). To separate an individual note in preparation for tuning, you can then press Tab until you locate the beginning of the note, Shift+Tab to select to the next note, and B to separate the note into a new region. Work your way through the part until you have separated all the notes you intend to retune. Note that in Pro Tools 8, Tab to Transient is much more sensitive (some say too sensitive) than in the previous version, so you may find it locating to events you don't consider transients.

Unlike AudioSuite processing, which names processed regions to reflect the process used, Elastic Audio does not reveal itself in region names. Once you've satisfactorily pitch-shifted a loop, you should immediately rename it to reflect its new pitch. If it's already selected, press Command+Shift+Option+R (Control+Shift+Alt+R); if not, double-click it with the Grabber (not the Separation Grabber) to open the Region Name dialog. If you've retuned individual notes, you'll first want to consolidate the loop by pressing Shift+Option+3 (Shift+Alt+3).

FIG. 3: Pitch shifting is controlled from the Elastic Properties window. You can raise or lower the pitch of a selected region by as much as two octaves in hundredths of a semitone (cents).

FIG. 3: Pitch shifting is controlled from the Elastic Properties window. You can raise or lower the pitch of a selected region by as much as two octaves in hundredths of a semitone (cents).

With vocals, you'll need to do more manual editing. When there's a clear BREAK between words or syllables, you'll have no trouble finding an edit that allows a natural-sounding pitch change, but trying to hide tuning edits in a legato phrase is more difficult. Always cut on zero crossings to prevent clicks. Short crossfades can help smooth the transition — because the waveforms are coherent, use the equal gain curve to prevent a volume bump. Tuning across a legato transition may simply be impossible with Elastic Audio. Win or lose, you'll quickly discover why auto-tuning software often struggles with such transitions (and why the so-called Cher effect is so easy to create with those plug-ins).

Once you've properly separated your regions, select the first region that requires tuning and press Option+5 (Alt+5) on the numeric keypad to open the Elastic Properties window (see Fig. 3). To audition the start of the region in context, press Command+Option+Left Arrow (Control+Alt+Left Arrow). Pro Tools will begin playback by the pre-roll amount before the region and continue past the region start by the post-roll amount. Pre- and post-roll do not need to be enabled, but they must be set to appropriate non-zero values. To audition the end of the region in context, press Command+Option+Right Arrow (Control+Alt+Right Arrow).

Enter the desired amount of pitch adjustment in the Elastic Properties window and then audition the results. If you use the mouse to drag the pitch-shift fields up or down in value, the cursor will remain focused on the track, allowing you to select the next region by pressing Control+Tab (Start+Tab). The workflow then becomes audition with the shortcut, tune with the mouse, audition to confirm, advance with the shortcut, and repeat. Because the Elastic Properties window floats, the mouse remains focused on the pitch-shift fields.

Establishing fluid procedures like I've described here allows you to work efficiently, saving you time and allowing you to remain focused on the creative judgments instead of the technical process. Pro Tools has always been designed to take maximum advantage of keyboard shortcuts — if you find yourself clicking around the interface a lot, you're making life harder than it needs to be. Study the keyboard shortcuts and analyze how they can help you.

One more shortcut introduced in Pro Tools 8 that will come in handy during this process is Shift+S to solo the current track. (Note that Shift+M mutes the current track.) Critical tuning requires being sure that the pitch sounds right in context with the other tracks, as well as being sure that the tuning didn't cause any artifacts or awkward transitions, so you'll want to solo each pitch change to confirm that it's clean.

Name That Tuning

You can also transpose regions on an Elastic Audio-enabled track from the Event Operations window. However, transposing by key or to a single pitch is not allowed, as these would require Pro Tools to know the original pitches. Looped regions cannot be transposed, although transposed regions can be looped. A quick workaround to transpose all looped iterations by the same amount is to press Command+Option+U (Control+Alt+U) to unloop the regions, which automatically flattens and selects the looped iterations. Transpose them as necessary, and then press Command+Option+R (Control+Alt+R) to reloop them.

FIG. 4: The clip indicator, to the left of the warp indicator, shows clipping caused by Elastic Audio processing. To prevent this, lower the input gain setting in the Elastic Properties window.

FIG. 4: The clip indicator, to the left of the warp indicator, shows clipping caused by Elastic Audio processing. To prevent this, lower the input gain setting in the Elastic Properties window.

The process of changing the pitch of a region can sometimes cause an increase in the region's highest peaks. Although this is not ordinarily audible, if it causes the peak to clip, then the resulting distortion can be quite disruptive. When that happens, a clip indicator appears to the left of the region's warp indicator (see Fig. 4). To mitigate this, the Elastic Properties window has an Input Gain field that allows you to adjust the region's gain prior to pitch processing. If you work with very hot samples on a regular basis, you can set a negative default input gain for all Elastic Audio processing in the Elastic Audio preferences.

Elastic Audio does not work with Sound Designer II (SDII) files. You should really be using Broadcast WAV (BWF) files anyway, as those have become the de facto industry standard. If you are working with an older SDII session or loop library, though, you'll need to force the audio to the session format. Fortunately, Pro Tools 8 allows LE and M-Powered sessions to use mixed file formats if necessary, something that was previously limited to HD systems. Don't mix formats unless you have to, however, as performance will suffer.

Pro Tools 8.0cs2 has a reported bug involving Elastic Audio and the Clear Selected command. When you select unused regions to clear them from your session, the underlying audio for Elastic Audio regions can sometimes be selected and subsequently deleted if you use the Clear, Delete command. Of course, with hard drive space getting ever cheaper, you have very little reason to be deleting files at any point. It's better to waste space on takes you think you'll never need than to risk losing something of value.

Although you may wish for an intelligent pitch-detection algorithm, Elastic Audio's pitch-manipulation capabilities offer a great deal of power. Wielded wisely, its toolset allows you to retune loops and massage vocals efficiently and with results that sound good. The key, as with any tool, is finding a workflow that lets Pro Tools do the work while you remain focused on the creative decisions.


Brian Smithers is department chair of workstations at Full Sail University and the author of Mixing in Pro Tools: Skill Pack from Cengage Learning.

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Manufacturer Contacts

Amidio, Inc. (Noise.io);

Audiodog (BPM Tap Tempo),

AudioRealism (Technobox);

Benjamin McDowell (Harmonica);

BIAS (iPRoRecorder);

Bitcount (Cleartune)

Far Out Labs (ProTransport and ProRemote)

Frontier Design Group (iShred, Guitar, Cowbell Plus);

Griffin Technology (iTalk Recorder);

Holger Meyer (Karajan);

Intua (BeatMaker);

ioMetics (GigBaby!);

iZotope (iDrum);

Massimo Biolcati (iReal Book);

Mauvilla Software (OmniTuner);

Music Motion (Metronome-iTick);

Normalware (Bebot);

Pure Profit (BtBx);

Reality Jockey (RJDJ); site will be changing

Retrolink HB (Randgrid Synthesizer and Drum Machine)

Retronyms (Recorder)

Roventskij (IR-909);

Silicon Studios (ITM MCU, ITM Keys);

Sonoma Wire Works (Four Track);

Sound Trends (Looptastic Electro Edition, Looptastic Progressive Edition);

Studio Six Digital, (SPL, SPL Meter, RTA, FFT, Generator)

Thezi Studios (Metronome TS); URL Not available

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