Sound Design Workshop: VocoVerb

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FIG. 1: In this Reason 4 Combinator, audio is routed through the DDL-1 and RV-7 to the Vocoder Carrier input. The dry signal is also merged to mono and used for the Modulator input.

You can create unusual reverb- and echo-like effects by following extreme reverb or feedback delay with a vocoder and using the dry signal as the vocoder's modulator. Of a vocoder's two inputs, the carrier is the signal being processed, whereas the modulator (sometimes called the program) is analyzed for its harmonic content. That analysis is used to filter the carrier so that only matching harmonic content gets through.

In the classic example of vocoding — robotic-sounding singing — speech is the modulator and a harmonically rich sound such as strings or a lush pad is the carrier. But vocoders are now put to all kinds of uses in sound design. I'll use the built-in vocoders in Propellerhead Reason 4 and Ableton Live 8 for my examples and provide templates from both applications in Web Clip 1.

The Hook-Up

In Reason, create a Combinator and insert a BV512 vocoder, a DDL-1 delay line, a RV-7 reverb, and a Spider Audio module. Create all modules with the Shift key held down because Reason's automatic wiring is not helpful here. Connect the Combinator's To Devices outputs to the Spider's Splitter inputs and then create a chain from a pair of the Spider's Splitter outputs through the DDL-1, through the RV-7, and into the vocoder Carrier inputs. Cable another pair of the Splitter outputs to two of the Spider's Merger left/mono inputs to create a mono mix of the incoming signal and cable that Merger output to the vocoder's Modulator input (see Fig. 1).

In Live 8, create an Audio Effects rack in an effects-return channel, insert Live's new Vocoder module in the default chain, and name that chain Modulator. Create a second chain, insert Simple Delay and Reverb modules in series in that chain, and name it Carrier. Set the vocoder's Carrier input to External and choose the Post FX (not Post Mixer) output of the Carrier chain as its source. You will ultimately want to mute the Carrier chain to suppress the dry signal from the output, but for setting up the delay and reverb, temporarily unmute the chain and deactivate the vocoder. (I set up a Macro knob to let me quickly toggle back and forth.)

The Tune-Up

You might use the delay, the reverb, or both to process the carrier. For choppy material such as a percussion or rhythm track, try the delay by itself and with no feedback. Set the delay time so as to shift the beat by an 8th- or 16th-note or the corresponding triplet, depending on the material. Then bring in some delay feedback or add some reverb and adjust the reverb tail to dial in the effect you want (see Web Clip 2). With drums, instead of using the whole track as the modulator, try just the kick drum or the snare.

The three critical vocoder settings in Reason (Live) are Shift (Formant), HF Emph (Enhance), and Decay (Release). Shift offsets the carrier bandpass filters relative to the modulator analysis bands. For example, if you're using only the kick drum as modulator, then a negative shift will bring out higher-pitched percussion. In Reason, you can also flip to the rear panel and remap the bands manually. HF Emph boosts the high-frequency end of the carrier, which often adds clarity. Decay refers to the envelope followers (virtual or real) used in the modulator frequency-band analyses. Increasing decay allows more of the carrier to ring through, an effect similar to increasing a reverb tail. Finally, the number of vocoder bands has a dramatic influence, and more is not necessarily better. Tweaking each of these settings will make its effect obvious.

For denser material such as long chords, pads, and ambient sounds, try delay times of 100 ms or less without reverb. Delays of a few milliseconds combined with high feedback produce resonator effects that add subtle color once they are masked by the vocoder. Automating the vocoder's shift or manipulating it in real time with a mod wheel is especially effective with resonator-like settings (see Web Clip 3).

To create a choral effect for vocals and instrumental tracks, use a tempo-synched delay with different settings for the left and right channels, and use a reverb with a fairly long tail. Then adjust the vocoder band count, shift, and decay settings as necessary (see Web Clip 4).

Finally, experiment with other effects along with or instead of delay and reverb. Distortion, flanger, chorus, phaser, frequency shifter, and beyond are all fair game. The purpose of the vocoder is to tame their more extreme aspects while retaining the original flavor.

Len Sasso is an associate editor of EM. For an earful, visit his Website