Adventures in Vocal Processing

Nov 1, 2006 12:00 PM, By Geary Yelton

Celemony Melodyne Studio 3.1

Melodyne Studio 3.1 (Mac/Win, $699) is the most comprehensive program for manipulating the pitch and rhythm of vocal tracks. The application lets you transpose and correct pitch; shift formants; alter tempo, rhythm, and duration; automatically create harmony voices; and otherwise edit audio as if it were MIDI data. Melodyne comes in three versions to suit your needs and budget; the top-of-the-line Studio 3 version works with polyphonic as well as mono files, making it an indispensable studio tool.

Most of the action occurs in Melodyne's Editor and the Arrange window. The Editor, which opens when you load an audio file, furnishes all the time-stretching, pitch-shifting, and related functions. The Arrange window resembles a traditional multitrack digital audio sequencer, and in fact, Melodyne can function as a rather basic audio sequencer. Double-clicking on any track in the Arrange window opens the Editor for that track. For the purposes of this article, then, the Editor is the more interesting window.

In the Editor, individual audio events are shown as Blobs on a grid that has a note ruler on the left (see Fig. 6). Each Blob's alignment with the note ruler indicates its pitch center. Its shape indicates its amplitude envelope, and its length indicates its duration. If you click on a Blob and drag it up or down, you transpose its pitch by semitones. If you also hold down the Alt (or Option) key, you can transpose it by cents, which is necessary for manual pitch correction. A scrub function allows you to hear the changing pitch as you drag the Blob. If you select Correct Pitch from the Edit menu, Melodyne automatically repairs any pitch errors by aligning pitches with any preset or user-defined scale.

You can also select more than one Blob at the same time and transpose them as a group. That technique is useful for generating harmony parts; just select the notes you want to harmonize and drag them up or down while pressing Shift + Alt. If you like, Melodyne can automatically introduce slight random pitch and timing variations, which helps to prevent comb filter effects and make harmonies sound more natural. Unless you want parallel harmony, you then select and transpose individual notes and groups of notes to adjust their intervals. If you first enable the Scale Snap function, however, the harmonies conform to whatever key you specify.

If Always Show Pitch Curve is enabled in the View menu, you'll see pitch curves superimposed on the Blobs. You can zoom vertically or horizontally to get a better look at a selected audio event or group of events. Zooming is especially handy when you're dealing with a large file or an entire song.

By default, Melodyne preserves an event's formants and amplitude so that its timbre and loudness don't change when you transpose its pitch. If you prefer, however, you can transpose formants, change amplitude, and modify other parameters just as easily as pitch, either by selecting the appropriate command from the Edit menu, by selecting one of several tools from a palette, or by right-clicking and selecting a tool from a contextual menu.

Melodyne offers numerous techniques for changing duration without affecting pitch or formant structure. If you enable Autostretch in the Transport Bar and change the entire file's tempo, all durations will be scaled accordingly. You can import tempo from a MIDI file, halve or double tempo from the Edit menu, and quantize an entire file. You can move a Blob's start or end point, which changes its duration, by clicking-and-dragging its left or right edge. If the audio is contiguous and one event leads immediately to another, manually changing duration affects the duration of events before or after the edited Blob. Changing the duration of a single event that has a rest before or after, however, has no effect on the duration of other events.

One of the most exciting features of Melodyne Studio 3 and later is the ability to work with polyphonic audio files, even an entire mix. When you load a mono or stereo audio file containing vocal harmony, Melodyne displays it as a series of Blobs lined up as if they were all one pitch. Transposing the pitch of any Blob keeps all harmony parts intact; when you pitch-shift an ensemble singing a chord, Melodyne transposes the entire chord rather than the individual voices (see Web Clip 6). Transposing polyphonic material is useful for correcting the pitch or changing the key or tempo of an entire song, or for introducing a tempo or key change at some point during the song.

Synchro Arts VocALign Project 2.9

Just as some software automatically corrects tuning, VocALign Project (Mac/Win, $375) automatically corrects timing discrepancies between two tracks. It works by performing a spectral analysis of both tracks and then applying variable time compression and expansion to make one line up with the other. Syncing tracks after they're recorded saves time by allowing a singer to concentrate on a good performance during an overdub, rather than on trying to duplicate a previous performance's timing.

VocALign matches the energy pattern variations of one track, called the Dub, to those of another track, called the Guide. You begin by dragging the Guide file into the upper display and the Dub file into the lower one (see Fig. 7). Because VocALign works with audio files no longer than two minutes, you're often better off working with small clips rather than song-length tracks. The Play menu lets you audition either file or both simultaneously. Clicking on the Align button superimposes an outline of the realigned Dub's pattern over the Guide's pattern. You can then audition the two synchronized tracks or the realigned Dub alone. Six presets let you choose how tightly the Dub will be aligned to the Guide. When you're happy with the results, click on the Edit button to save the realigned Dub as a new audio file (see Web Clip 7). VocALign automatically names it and places it in a folder of your choosing.

Thanks to cooperation between Synchro Arts and MOTU, VocALign Project also works from within Digital Performer (DP). First select an audio track, and then open the VocALign submenu in DP's Audio menu to specify it as the Guide. Select another track as the Dub, and then realign the Dub by choosing Align and Spot Audio from the same submenu. Two additional versions of VocALign are available as plug-ins for Pro Tools users, the AudioSuite plug-in VocALign Project for Pro Tools (Mac/Win, $375) and the RTAS plug-in VocALign Pro 4 (Mac/Win, $629 download, $699 boxed).

TC-Helicon Intonator HS

To use Intonator HS or VoiceModeler, you'll need a TC Electronic PowerCore, a hardware-based DSP accelerator that's available as an expansion card or as an external processor. Intonator HS (Mac/Win, $249) is a plug-in that specializes in pitch-correcting vocal tracks. Borrowing algorithms from TC-Helicon's respected line of voice-modeling hardware products, Intonator HS can shift pitch a maximum of six semitones up or down so that it conforms to a preset scale or to your real-time MIDI input. It uses a Hybrid Shifting algorithm (hence the HS in the name) to effectively retain a natural vocal sound even when transposing as much as half an octave.

Intonator HS's pitch meter indicates the input signal in red and how sharp or flat it is by its deviation from the center (see Fig. 8). When correction is enabled, it indicates the amount of correction in blue. You can select optional meter views, such as only the output pitch or the amount of correction. The keyboard has 12 buttons for selecting the key signature, the notes of a custom scale, or a single note in Manual mode. Other controls let you vary the amount of correction, control the speed at which correction is applied, and remove rumble and hum with a low-cut filter. A unique manual pitch-bend wheel lets you vary pitch in real time, but you can't assign your MIDI controller's pitch bender to control it, nor can you change the wheel's 12-semitone range.

The Scale/Mode pop-up menu determines the pitches that the corrected notes will adhere to; you can choose from 47 preset scales and specify 3 user-defined scales. The Custom Scale setting allows you to select which of 12 pitches to include. In Manual mode, you can select a pitch to be corrected by clicking on the keyboard, which is most useful when only a single pitch is causing problems.

Intonator HS's straightforward user interface makes it easy to quickly see and control what's going on. Probably because it's optimized specifically for vocals and has a limited range of pitch-shift, the plug-in does an outstanding job of minimizing audible artifacts and glitches (see Web Clip 8).

TC-Helicon VoiceModeler

Another PowerCore plug-in from TC-Helicon, VoiceModeler (Mac/Win, $249), also duplicates specific capabilities of TC-Helicon's voice-modeling hardware. VoiceModeler can alter voices either subtly or dramatically, making a male voice sound female, for example, or a thin voice sound throaty. The singer's vocal dynamics can control parameters such as breath and growl, allowing you to change a performance's expressive qualities at will. You can dial in a variety of vocal personalities and build an entire choral ensemble from a single voice. VoiceModeler lets you transform a voice's timbral qualities in much the same way you use a synth plug-in to manipulate instrumental sounds.

The best way to discover VoiceModeler's capabilities is to explore its 16 presets. You can easily modify their settings and save your edits as new presets, or you can create your own presets from scratch. VoiceModeler's most essential settings are in the Effect section, which has a Bypass button, a Style menu, and sliders that control depth for each of six Effect parameters: Resonance, Spectral, Breath, Growl, Inflection, and Vibrato.

Resonance controls harmonic content by emphasizing positioning within the vocal tract; some Styles exhibit a deep chest resonance, for instance, and others resonate in the throat or the sinuses. The Spectral parameter is intended to emulate a singer's natural tone control. You can modulate the Spectral and Resonance parameters using VoiceModeler's Modulation section, which supplies independent depth knobs for both destinations and an LFO that can sync to tempo.

Breath presets range from relatively subtle Styles such as Natural, Soft Air, and Medium Rough to the more extreme Dark Whisper, Phlegmy, and Tracheotomy. Growl lets you impart a voice with graininess and grit. The Inflection control is multifaceted, offering gender-bending effects, randomization, and various types of scooping (see Web Clip 9). Vibrato adds periodic variations in pitch and amplitude and furnishes presets for different musical genres.

A graphical display takes up about a third of VoiceModeler's control panel. It provides a continuous visual representation of each parameter's effect on the source, allowing you to quickly grasp how each of the six Effect parameters contributes to what you hear (see Fig. 9).