Spice Up Your Tracks with a Vocoder

Vocoders Used to Be Expensive and Super-Complex - But No More

by Craig Anderton

Heard any robot voices lately? Of course you have, because vocoded vocals are all over the place, from commercials to dance tracks. Vocoders have been on hits before, like Styx’s “Mr. Roboto” and Lipps Inc.’s “Funky Town,” but today they’re just as likely to be woven in the fabric of a song (Daft Punk, Air) as being applied as a novelty effect. So, let's take a look at vocoder basics, and how to make them work for you.

VOCODER BASICS

Vocoders are best known for giving robot voice sounds, but they have plenty of other uses. A vocoder, whether hardware or virtual, has two inputs: instrument (the “carrier” input), and mic (the “modulation” input). As you talk into the mic, the vocoder analyzes the frequency bands where there’s energy, and opens up corresponding filters that process the carrier input. This impresses your speech characteristics onto the carrier’s signal.

Clockwise from top: Reason BV512, Waves Morphoder, Ableton Live Vocoder, Apple Logic Evoc 20

Some programs, including Cubase, Logic, Sonar, Reason, and Ableton Live bundle in vocoders. However, until recently, the ability to sidechain a second input to provide the modulator (or carrier) was difficult to implement. Two common workarounds are to include a sound generator within the plug-in and use the input for the mic, which is the approach taken by Waves’ Morphoder; or, insert the plug-in in an existing audio track, and use what’s on the track as the carrier.

VOCODER APPLICATIONS

• Talking instruments. To create convincing “talking instrument” effects, use a carrier signal rich in harmonics, with a complex, sustained waveform. Remember, even though a vocoder is loaded with filters, if nothing’s happening in the range of a given filter, then that filter will not affect the sound. Vocoding an instrument such as flute gives very poor results; a guitar will produce acceptable vocoding, but a distorted guitar or big string pad will work best. Synthesizers generate complex sounds that are excellent candidates for vocoding.
• Choir effects. To obtain a convincing choir effect, call up a voice-like program (e.g, pulse waveform with some low pass filtering and moderate resonance, or sampled choirs) with a polyphonic keyboard, and use this for the carrier. Saying “la-la,” “ooooh,” “ahhh,” and similar sounds into the mic input, while playing fairly complex chords on the synthesizer, imparts these vocal characteristics to the keyboard sound. Adding a chorus unit to the overall output can give an even stronger choir effect.
• Backup vocals. Having more than one singer in a song adds variety, but if you don’t have another singer at a session to create “call-and-response” type harmonies, a vocoder might be able to do the job. Use a similar setup to the one described above for choir effects, but instead of playing chords and saying “ooohs” and “ahhhhs” to create choirs, play simpler melody or harmony lines and speak the words for the back-up vocal. Singing the words (instead of speaking them) and mixing in some of the original mic sound creates a richer effect.
• Cross-synthesis. No law says you have to use voice with vocoder. For a really cool effect, use a sustained sound like a pad for the carrier, and drums for the modulator. The drums will impart a rhythmic, pulsing effect to the pad.
• Crowd sounds. Create the sound of a chanting crowd (think political rally) by using white noise as the carrier. This multiplies your voice into what sounds like dozens of voices. This technique also works for making nasty horror movie sounds, because the voice adds an organic quality, while the white noise contributes an otherworldly, ghostly component.
• Don’t forget to tweak. Some vocoders let you change the number of filters (bands) used for analysis; more filters (e.g.,16 and above) give higher intelligibility, whereas fewer filters create a more “impressionistic” sound. Also, many speech components that contribute to intelligibility are in the upper midrange and higher frequencies, yet few instruments have significant amounts of energy in these parts of the frequency spectrum. Some vocoders include a provision to inject white noise (a primary component of unpitched speech sounds) into the instrument signal to allow “S” and similar sounds to appear at the output. Different vocoders handle this situation in different ways.

The days when vocoders were noisy, complicated, expensive, and difficult-to-adjust hardware boxes are over. If you haven't experimented with a software vocoder lately, you jut might be in for a very pleasant surprise.

Craig Anderton is Executive Editor of Electronic Musician magazine. He has played on, mixed, or produced over 20 major label releases (as well as mastered over a hundred tracks for various musicians), and written over a thousand articles for magazines like Guitar Player, Keyboard, Sound on Sound (UK), and Sound + Recording (Germany). He has also lectured on technology and the arts in 38 states, 10 countries, and three languages.