Roadside picnic — a dark, eerie drone synthesizer

Roadside picnic employs a ring networks of FM to produce eerie, dark drones and soundscapes.

The basis of the patch is ring FM — this is where instead of a single relationship between carrier and modulator, all of the oscillators become both carriers and modulators for one another. For instance: oscillator 0 FMs oscillator 1, which FMs oscillator 2, which FMs oscillator 3, which FMs… oscillator 0 — a ring! (And yeah, I numbered the oscillators in this patch 0 – 3; the numbers aren’t really significant.) While simpler carrier to modulator relationships can produce a wide range of timbres, from mellow to bell-like to metallic, the inherent instability of a ring design leads toward inharmonic, complex timbres — lots of distorted tones and growling waves. (Good stuff.)

Roadside picnic employs two such ring networks (named alpha and beta in the control set), as well as a feedback network. Each oscillator also passes through a VCA controlled by a looping envelope before directed at the other oscillators; this arrangement can produce some complex modulation outcomes, as the FM amount directed toward other oscillators rises and falls with the source’s own amplitude.

The oscillators’ frequencies can be driven into the sub-audio range. The original rationale for this was that at sub-audio rates, FM becomes more like a (very weird) vibrato, which is true, but one of the more delightful discoveries in doing so was that even when all of the oscillators are in sub-audio ranges, the patch still produces sound, as the FM sidebands’ harmonics continue to reach audio frequencies, but the results are more rhythmic than harmonic in nature, since the oscillators’ frequencies control how often those sidebands reach the audio range.

One of the more interesting features of the patch (that I’m sure you will see me play with again) is a “chaos modulator” — this is a shift-register-based modulation source, which random rate modulation. Because it’s a shift-register, its modulation evolves and changes over time, which makes it the perfect companion to a drone patch, which can get stale easily. (I detailed a variation of this idea in my third video/patch on sample and holds, if you’re interested in learning more:

Finally, the patch employs some noise modulation, filtering, and reverb to add additional effects to the core drone voice.

(The patch is named after a book I have not read, which Tarkovsky’s Stalker is loosely based on; Stalker was the original title of the patch, but I decided the name had too many negative connotations. If you’ve read this book, would you recommend it? Let me know.)


Across the top are the frequency controls for the four oscillators (0-3) used in the patch. The oscillators are panned across the stereo field.

Below these are the individual envelope length controls for each voice. The envelopes are equal-length attack/decay envelopes. You can get anything from long, slowly unfolding envelopes to audio-rate/ring mod stuff. The envelopes govern the output VCA of each voice, which is also where the FM connections are derived from, so the envelopes have a direct effect on how the other oscillators are modulated via FM.

The Bleed control mixes the envelopes with unmodulated signal. At 0, all of the voices’ outputs are determined by their envelopes. As Bleed is increased, the envelope still affects the output, but some of the audio passes through, regardless of the envelope. At 1, the envelopes have no effect, and the output just drones without modulation.

On the next row are the FM controls. Feedback controls how much of the oscillator’s output is fed back on itself. In general, this will amplify and intensify the effect of the other feedback networks. Crossfeed alpha and crossfeed beta control the two ring networks. Each one feeds the output of an oscillator into a different oscillator, so there are two ring networks that can be active at a time. The only oscillators that don’t affect one another, directly, via FM are the odd and even pairs of oscillators.

On the fourth row are the controls for the chaos modulator. Rate sets the base rate for the modulator, with small values providing the slowest rates. The rate mod randomly affects that rate per clock cycle, making the modulator speed up and slow down. The shift rate governs how often the values used by the shift register are exchanged for new ones, with higher rates leading to more variety.

The chaos modulator can be sent to either pair of oscillators — even or odd. Each has a bipolar amount. The chaos modulator is, itself, bipolar, so negative amounts will invert it (it will modulate the oscillator groups’ frequencies in opposite directions, for instance, if one amount is inverted and the other is not).

While the chaos modulator is designed to… well… bring chaos, when used more subtly, can it can add an interesting vibrato/pitch modulation to the voices, which keeps them more interesting without being obtrusive.

On the bottom row are additional effects.

Noise mod modulates the oscillators with digital noise (random module). This can add some “grit” to the voices and make them more unstable.

Corrosion modulates the carrier VCAs with digital noise, too. This introduces crackles, volume drops, downsampling artifacts. Busted radio stuff (although it sounds a bit like a Geiger counter, which was a big part of why I added it). As the carrier VCAs also control the FM connections, this has an affect on the FM settings as well.

The high and low-pass filters can be used to shape the sound. This patch can produce a -lot- of low-end, so a high-pass filter was necessary. It can also produce a lot of… grating high harmonic content, so a low-pass filter was necessary as well. But more than just filtering out unwanted noise, they can really transform the output. There is also a resonance control, which can do even more to transform the output as the modulating harmonics are picked up by the filters’ resonances, at both high and low frequencies.

Finally, there are decay and mix controls for a plate reverb, which adds ambience but also helps give the patch more cohesion.

And that’s it… another droner for the droners. I’m developing a nice little collection of these kind of cinematic, drone-y patches, I think.

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  • Category: Synthesizer
  • Revision: 1.0
  • License: Creative Commons Attribution Share Alike 4.0
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  • Modified: 3 months ago
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