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That Classic Vocoder Sound

Using Logic Pro 7's EVOC 20 PS Vocoder to play a vocal through your keyboard By Frank Moldstad

Although the Vocoder was originally developed in 1939 for secure communications, popular music has kept the technology alive in ways that could not have been envisioned by creator Homer Dudley. After EMS released the first commercially available Vocoders in 1976, recording artists from Kraftwerk to Stevie Wonder began using them to generate synthesized speech effects in their songs.

The Vocoder is  a classic sound that still pops up on contemporary releases, especially Electronica and Hip-Hop material. But these days, instead of a suitcase-sized piece of hardware, the Vocoder is likely to be a software application such as the EVOC 20 PS that is included with Apple’s Logic Pro 7. The EVOC 20 PS actually combines a Vocoder with a polyphonic synthesizer, and it can be played in real time using an external controller keyboard. Any notes that are depressed will use the audio clip as their sound source, whether they’re chords or single notes.

Although any audio source can be filtered through the EVOC 20 PS, its application is most dramatic with the human voice. In this tutorial, we’re going to walk through the process of using the EVOC 20 PS Vocoder to process a short vocal clip that could be used as a repetitive layered texture in a mix.

The first step is to find a suitable vocal clip. I used Logic Pro 7’s built-in Loop Browser [Audio>Loop Browser] to search my computer, settling on an Apple Loop from the Remix Tools Jam Pack called “House Music Female Vox.” I liked it because the duration was relatively short, which would be good for a repeating phrase.

But you can use any clip, of any duration, for processing through the Vocoder. When you decide on an audio file that you want to use, import it into an empty audio track in Logic Pro 7 by highlighting the desired track in the Arrange window and choosing Import Audio File from the drop-down Audio menu.  

Next, you need to insert the EVOC 20 PS into an Instrument track. To do this, click the empty gray slot under I/O on any Instrument channel in Logic’s Mixer window, and navigate to the Stereo folder, where all of Logic’s built-in instruments can be accessed. This procedure is the same whether you’re inserting a soft synth or the Vocoder. When you select the EVOC 20 PS, its interface appears.

Inserting EVOC 20 PS

Selecting Side Chain
On the EVOC 20 PS interface, click the gray box at the top under the words Side Chain. A long track list will drop down. Choose the audio track where you have inserted your clip. This routes the audio signal through the EVOC PS 20 input as a side chain.

You’re almost ready to begin Vocoding!

The only thing left to do is mute the audio clip’s  mixer channel. This can be done in either the Track Mixer or the Environment Mixer (whatever you do, don’t try muting the track in the Arrange window or you won’t hear anything.)

Arrange window showing looped audio track at top, EVOC 20 PS interface in middle and MIDI track at bottom with recorded Vocoder output.

Now press play. Hit a few keys on your keyboard, and you’ll hear that distinctive Vocoder sound. If you’re using a vocal clip to feed the Vocoder’s side chain input, you can make talking music! But the EVOC 20 PS also has an extensive set of controls for tweaking the sound. These include Synthesis, Sidechain Analysis, Format Filter, Modulation, U/V Detection, and Output. The best way to learn their functions is simply to experiment. If you mess the sound up somehow and can’t figure out what you did, you can always restore the default settings to get back to square one.

Below is a before-and-after comparison of the vocal loop I ran through the EVOC 20 PS. This MP3 file first plays the normal unadorned voice singing, "Come on baby feel the vibe, let me take you on a ride." Then the same loop is played through the Vocoder. One thing you'll notice is that the melody is different in the vocoded version. That's because it followed a simple chord change I played on the controller keyboard.

before after.mp3


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Related Keywords:Logic Pro 7, Apple, EVOC, vocoder, soft synth, synthesizer, Jam Pack

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  • That Classic Vocoder Sound by DMN Editorial at Feb. 18, 2006 3:21 am gmt (Rec'd 3)

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