How To: Envelopes as LFOs

Increase your modulation capabilities with these tips.
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Without modulation resources, a synthesizer is just a sophisticated organ. Modulation breathes life into a sound, adding motion to oscillators, filters, and amplifiers. Naturally, sound designers want as many options as possible for modulating synth parameters, but as is often the case with instrument design, pleasing every user equally is a daunting task: Some users want oodles of envelopes; others want LFOs galore.

What’s more, the feature set of a synth is a core component of its overall sound. While it’s fun to fantasize about softsynths and modular rigs having unlimited possibilities, the instruments that stand the test of time have a particular sound. And that sound is partially defined by the modulation tools that are available.

This month, I will demonstrate ways to use envelopes as LFOs. Not every synth supports this level of versatility, but quite a few mainstream products—both software and hardware—do. Here are techniques for three of the most popular synths available now.

MOOG SUBSEQUENT 37

The Subsequent 37 may be one of the most prevalent Moogs ever, thanks to its array of modulation amenities, including two loopable DAHDSR (delay, attack, hold, decay, sustain, release) envelopes. Because of the extra envelope segments, you can create both classic waveshapes and complex parameter articulations that would be impossible to duplicate using standard LFOs.

The rate of the modulation, of course, is determined by the envelope segment times. For example, it may seem intuitive that a triangle wave is created by adjusting attack and decay times—leaving the sustain at zero—but to dial in the correct speed, you’ll have to increase each of their times accordingly. To get started, turn on the envelope Loop parameter (Figure 1). A slightly resonant, low filter cutoff frequency with 30% to 50% envelope depth offers the clearest sonic representation of the shape, but from there you can experiment with the amp envelope and other options.

Fig. 1

Fig. 1

ABLETON LIVE WAVETABLE & OPERATOR

Live’s Operator was one of the first softsynths to popularize looping envelopes, which sound fantastic in the context of FM synthesis. Live 10’s new Wavetable also includes this feature for all three of its freely assignable envelopes (Figure 2). The only difference between the two synths is that Operator allows the envelope loops to be synchronized to tempo—perfect for creating rhythmic effects—while Wavetable’s envelopes are entirely dependent on their segment times.

Fig. 2

Fig. 2

That said, Wavetable’s envelopes offer adjustable curves and assignable values for start level, peak level, and final level, giving it the edge for unusual shapes. For example, this looping Wavetable envelope in Figure 3 would be nearly impossible to create via traditional LFOs. Applied to pitch, this type of contour (with very subtle modulation amounts, controlled via the mod wheel or aftertouch) will yield pitch articulations that are normally the territory of acoustic instruments like violin or flute. Alternately, applied to parameters like cutoff or wavetable position at greater depths, it’s useful for wild timbral shifts that can be handy for electro or complextro styles.

Fig. 3

Fig. 3

PROPELLERHEAD THOR

Available both in Reason and as a standalone iOS app, Thor is another classic softsynth with looping options for both the modulation envelope (per voice) and global (paraphonic) envelope (see Figure 4). Moreover, the duration for each segment can also be synchronized to tempo. The main difference between these envelopes is that the global envelope is based on a DAHDSR configuration, so it can also re-create square and pulse LFO waveforms.

Fig. 4

Fig. 4

To experiment, set the attack, decay, sustain, and release segments to zero, and then assign the envelope to oscillator pitch. From there, adjust the delay and hold segments to vary the duration for the “down” and “up” sections of the pulse, respectively, with equal values delivering a square wave.

Note that Reason’s new Europa and Grain synths also offer envelope looping, but with nearly unlimited breakpoints for designing complex shapes.

Next month, we’ll invert this concept and apply LFOs as envelopes.