Adjusting the pitch of a recording has always been a complicated matter. We’re not talking about correcting pitch note by note; rather, we’re talking about changing pitch and timbre up or down by ±12 semitones (50-200 percent). Most likely, changing pitch will result in speeding or slowing the audio, which will alter the overall timeline and change the timbre of an instrument. Altering pitch without affecting the timeline usually necessitates a tool that can analyze audio offline, and then apply changes. Sony Acid Pro 7, Ableton Live 8 and Steinberg Cubase 5 have each adopted zplane’s élastique pitch-shifting engine, which provides smooth real-time pitch alteration. Now, thanks to the Élastique Pitch plug-in, zplane’s phase and timbre preserving pitch adjustment tool is available for Pro Tools in RTAS form.
The fact that this tool provides real-time pitch shifting is not necessarily its biggest draw. The software’s most interesting aspect is the ability to easily shift pitch and timbre independently of one other. Its interface lets users link the individual sliders corresponding to each of these fields and, in doing so, perform more-familiar pitch shifts. However, a new realm of possibilities is introduced when breaking the link between pitch and timbre. The timbre slider allows shifting of formants, or the buildups of certain frequencies specific to a sound source. For example, when an individual speaks, certain natural resonances are produced by the specific characteristics of that person’s vocal tract. Each musical instrument has a similar pattern of formants that create the sonic essence of that instrument. To shift the entire pitch of a recording would result in shifting these formants, thus compromising the true sound of that instrument.
That is the beauty of Élastique Pitch. It allows the user to shift the pitch of all of the overtones of a recording, while still maintaining the frequencies of the formants. And with that, the opposite is also true. You can create a shift in frequency from an A scale to a C scale, while still having it sound like the same person singing it. Likewise, the speech of a person with a short vocal tract can be shifted to sound like a larger person, while preserving pitch and time. The result is a tool that’s a welcome addition to the toolkit of engineers who work in both music and sound design. Possibilities include pitch-shifting a baritone sax while still making it sounding like a baritone sax, or creating creature vocals by dropping the timbre while still remaining in an intelligible vocal frequency range.
The plug-in’s manufacturers also recognized the value of this tool in another aspect of post-production. Included in the interface are presets for pitch correction of soundtracks altered in speed by transfers across mediums. All of the standard pull-ups/pull-downs are accounted for, including 24 fps to 25 fps for transferring North American film to PAL and 24 fps to 23.976 fps for transferring North American film to 3:2 pulldown NTSC video, among others. Other controls include an input-select switch that lets users determine the frequency range of the formants considered for preservation.
Great GUI and More
The user interface is slick. It looks particularly cool in the “dark” skin, which is not the default, but an available selection. A real innovation in the plug-in window is the ability to scale the interface, so you can make it big enough for precise control, but then back it off in size to take up less space in your workspace. It seems that this code may have caused a glitch, however, because opening multiple instances of the plug-in simultaneously results in the GUI and the actual plug-in window being severed.
MIDI control is another potentially cool feature. At present, keystrokes from a MIDI keyboard reflect as changes in pitch; however, there is no sustain. In other words, pressing a key changes the pitch, but letting go results in a return to the original pitch. It would be nice if there were some parameters to hold the last note until a new key is struck.
Élastique Pitch is exceptionally smooth in its real-time pitch shifting. The plug-in responds to automation in Pro Tools. The pitch and timbre can be automated independently or linked in automation. The only cost is considerable latency (approximately 7,000 samples on my M-Powered 7.4 system running on a MacBook 2.16 Core Duo with 2 GB of RAM), though I was pleasantly surprised with the manual’s thorough instructions for overcoming this problem. In addition, the latency didn’t increase when jumping to a stereo multichannel version.
My biggest complaint would be that clicking the plug-in window behaves
like clicking on another application. If you click on the plug-in
interface to tweak a setting, you have to click on the Pro Tools mix or
edit window before initializing a transport command. You dial in a
setting, hit spacebar to play, and the OS just “dings” with the error
sound unless you click back into the Pro Tools interface first. This is
easily overcome by transporting from a control surface, but a tad
annoying when working with just a mouse and keyboard and making
frequent changes to the plug-in interface. These are minor complaints,
however, which I look forward to seeing resolved in later revisions.
To my ears, the plug-in sounds great (for audio sample
files that you can download for comparison, see "zplane Élastique Pitch Plug-in Audio Samples" below). With any sound source that
I tested it on, from full-frequency final stereo mixes to monotone
spoken-word vocals, the artifacts rarely limited any reasonable sonic
possibilities. I didn’t try the plug-in on anything more than a stereo
track, but the literature says that it can be instantiated on tracks
with up to eight channels (i.e., 7.1). I’m sure that I will find the
formant preservation while shifting pitch, or the creative potential
offered by the ability to shift timbre freely, to be indispensable now
that they’ve become available.
Moreover, zplane has no need to prove itself, as the company has
already been accepted into the workflow of countless audio
enthusiasts—whether these users realize that their favorite DAW is
using the élastique engine or not. The real news is that this tool has
now become available to professionals centered in the Pro Tools world,
and it will be exciting to see the software evolve in the RTAS arena.
For more information, visit zplane’s Élastique Pitch plug-in page.
Brandon Hickey is a recording engineer based in Chicago.
zplane Élastique Pitch Plug-in Audio Samples
The following WAV files can help you judge for yourself how well élastique works in relation to Digidesign's TCE (time compression/expansion) DigiRack plug-in for Pro Tools HD systems.