The ELS Vocoder, a classic software vocoder emulator, comes with several hundred factory presets.
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In ELS Vocoder, basic controls for all modules are accessible on a single control panel. The wedge at the bottom right of each module reveals a panel of expert controls.

ELS Vocoder ($279) from Eiosis (formerly Eliosound) is about as classic as it gets when it comes to software vocoder emulations. It starts with a bank of bandpass filters coupled with envelope followers that analyze incoming audio (called the modulator) for the level of each frequency band. It uses this analysis to set the band levels of another bank of bandpass filters, which are used to process a different source (called the carrier). The modulator is usually speech, but any rhythmic, harmonically rich sound works well. A built-in 2-oscillator synth is provided for the carrier. The built-in synth is basic, but with an upcoming sidechain feature (which should be available by the time you read this), you can use anything in your audio library or arsenal of soft synths for the carrier.

ELS Vocoder comes as an AU, VST, and RTAS plug-in for both the Mac and PC. I tested it in a variety of host sequencers on a dual 2 GHz Power Mac G5. It is a great-sounding and versatile plug-in, but it is CPU intensive. A single instance using the built-in synth as the carrier (the least CPU-intensive option) easily pushed the CPU meter past 40 percent in Ableton Live 6, Steinberg Cubase 4, and Apple Logic Pro 7.

Analyze This

The vocoder's analysis section offers a few pleasant surprises. An attack-release envelope follower lets you gate the modulator with separate opening and closing thresholds. That's especially useful when using drum and percussion tracks as the modulator.

An optional pitch follower will analyze the pitch of the modulator, and you can use its output to modulate the frequency of the synth's oscillators and LFOs as well as that of a frequency-shifter effect at the vocoder's output. That's handy when the modulator is a monophonic vocal or instrumental (see Web Clip 1). As with most vocoders, a voiced/unvoiced (V/UV) detector is provided to toggle the carrier between the synthesizer and a noise generator, and you can apply the pitch follower to the whole signal or only the voiced part. You can also quantize the pitch follower's output to semitones.

Most notably, the analysis filter bank, which you can configure with 20 or 22 bands, has a full-fledged mapping matrix. With that you can map any combination of analysis bands to control each processing band. Furthermore, each processing band has its own level meter and fader.

You can assign the MIDI Sustain pedal (CC 64) as well as either of the vocoder's two LFOs to freeze the analysis in its current state. You can apply freezing separately to the band levels, the V/UV status, and the pitch follower. Freezing by an LFO synced to host tempo adds an interesting rhythmic twist to vocoding.

Synthesize That

The built-in synth has two multiwaveform oscillators, and each has a static resonant lowpass or shelving filter. You can frequency and pulse-width modulate each oscillator with either of the two LFOs, the other oscillator, or noise. The oscillators are tunable in octaves, semitones, and cents; they can track the pitch follower; and they can be always on or gated by the V/UV detector. The lack of an envelope for the filter is a slight drawback of this otherwise capable synth.

The synth responds to incoming MIDI, and a 3-octave keyboard is provided for triggering the synth with the mouse. (Oddly, the keyboard range cannot be shifted.) In a nice touch, right-clicking or Shift-clicking on a note holds it on until clicked again. You can configure the keyboard as 16-voice polyphonic; monophonic; or 2-, 4-, or 8-voice detuned unison. Held notes are saved with vocoder presets, allowing you to save patches along with chords to play them.


A frequency shifter (a single-sideband ring modulator) is available at the end of the vocoder's signal path, and you can feed it the full output or just the modulator, carrier, or vocoded signal. You can set output levels and pan positions independently for the dry signal, the lower sidebands, and the upper sidebands using the frequency shifter's back panel. It's unusual to find a frequency shifter on any synth, and being able to apply it to the incoming audio or the built-in synth is a welcome addition to this plug-in's bag of tricks.

ELS Vocoder comes with several hundred factory presets spread across 19 banks. That's plenty to get you started, and you can, of course, create your own presets and banks. Separate A and B memory slots allow you to compare presets quickly, which is handy when you're making incremental modifications. You can download a feature-limited demo from the Eiosis Web site, and it's worth your time to give it a spin.

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