Master Class: Pitch Shifting in Pro Tools 8

Jun 1, 2009 12:00 PM, By Brian Smithers

           
 

EXPLORING ELASTIC AUDIO'S NEW DIMENSION

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.

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.