Anyone who works with audio samples knows how important time-stretching and pitch-shifting can be in getting your sounds just right. Nearly every audio editor offers some form of these two DSP algorithms, but they are likely to be fairly basic and have limited effective ranges. To address these tasks more professionally, Wave Mechanics has released Speed, an AudioSuite plug-in that lets you change the pitch, length, and tempo of your audio files. It’s one of only a few dedicated programs that offer these features, and it can be just the right tool in many situations.

Speed doesn’t require that you have any TDM hardware—all you need is Pro Tools or other software that supports the Digidesign AudioSuite plug-in standard (Emagic’s Logic Audio, for example). I tested Speed using Pro Tools 5.01 on a Power Mac 9500 with a 300 MHz Crescendo G3 processor upgrade card loaded with 192 MB of RAM. Among the plug-in’s several user interfaces is the Simple control panel, which makes working with Speed nearly automatic. You can also switch the display to the Calculator or Graphical screen (more on those features later).

Speed Zone

FIG.1: Speed’s Simple control panel, one of the plug-in’s several interfaces, has knobs for controlling a sample’s pitch and tempo. The Preview feature is an excellent way to get an idea of how the processing will sound.

To use the plug-in, first select an audio range in the Pro Tools Edit window, then choose Speed from the AudioSuite menu. The default control panel, Simple, will appear (see Fig. 1). The Preview button at the bottom of the window lets you audition the current tempo and pitch settings (the default settings signify no change to your audio). Clicking on the Process button initiates DSP processing of your selected audio and saves the results to disk.

You use the Speed Control knob (on the left) to change tempo without altering pitch, and the Pitch Control knob (on the right) to change pitch without altering tempo. You can also click on the displayed value and type in a new setting. Both Speed Control and Pitch Control have different modes, which you select by clicking on the small white triangular Mode Select tabs in the middle of the window.

Speed Control has two modes: Tempo and Length. A Tempo setting above 100 percent increases the tempo, and a setting below 100 percent reduces the tempo. For example, a Tempo setting of 200 percent will result in a tempo twice as fast as the original, and a setting of 50 percent will give you a tempo half as fast. (Settings for Tempo and Length range from 50 to 200 percent, with a resolution of six decimal places in Simple and Calculator mode and three decimal places in Graphical mode.) In Length mode, higher settings lengthen a selection, resulting in a slower tempo, and lower settings shorten the selection, creating a faster tempo. As with Tempo mode, a 100 percent Length setting has no effect on the audio.

Pitch Control has three modes: Cents, Semitones, and Percent. Both Cents and Semitones let you shift your audio a maximum of one octave in either direction. Percent mode uses a frequency ratio to define the change; a value of 100 percent, for example, won’t modify the pitch. (Settings range from 50 to 200 percent.) This mode resembles the pitch-ratio control of older hardware pitch-change devices and can compensate for the pitch change produced by sample-rate conversion.

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Reprinted with permission from Magazine, December, 2000
© 2000, Intertec Publishing, A Primedia Company All Rights Reserved