Sound Design Workshop: Emulating Analog Behavior

September 7, 2017

Even in 2017, some softsynths still get a bad rap for sounding too clinical or clean compared to their analog cousins. Although there are numerous modern plug-ins that offer extremely detailed circuit modeling, if you’ve got a softsynth with a sound you already love, there are several ways to give it more of an analog character. It’s just a matter of using the right sound design techniques.

This month, we’ll look at four ways to add a touch of that analog chaos—both in tuning and timbre—to your original patches.

Fig. 1. Adding slight offsets to each oscillator’s keyboard tracking will help create the illusion of inconsistent control voltages.

KEY TRACKING

If you’ve ever used a tuner on a volt-per-octave synth, you’ve probably noticed that the oscillators can be surprisingly out of tune at the extreme octaves, even though the middle range sounds fine—or vice versa. Some synths, like Propellerhead Thor, give you the option of adjusting keyboard scaling on a per oscillator basis, with 100% representing proper tuning across the range.

To replicate the behavior of a vintage VCO, set this parameter to 98-99% (or 101-102% if your softsynth supports it) on one or more oscillators.

Fig. 2. Xfer Serum’s Chaos modulators are a great way to emulate oscillator drift.

LFOS

If you don’t have key tracking available, try adding an almost imperceptible amount of sine or triangle LFO to pitch—at the slowest possible rate—to only one of your oscillators. This technique simulates the subtle pitch drift of decaying analog oscillators.

If possible, turn off LFO retriggering so that the LFO is constantly in motion regardless of whether a key is pressed. Make sure that tempo sync is also turned off. If two LFOs are available, set each to a different oscillator with slightly different depth and rate values.

Pro Tip: If your LFO offers a Lorenz or a smoothed random option, use that waveform instead for more organic results.

VELOCITY

Fig. 3. By applying small amounts of velocity modulation to pitch and/or filter cutoff, you can simulate the behavior of voice cards that are miscalibrated.

Many iconic analog polysynths relied on several voice cards—one for each voice. It was common for these cards to fall out of calibration over time, making each voice sound slightly different from the others.

To simulate this effect, add a tiny amount of velocity sensitivity (either negative or positive) to the tuning of one or more oscillators, as well as the filter cutoff. The secret is to keep the amount of velocity modulation at its bare minimum. While the result won’t cycle repeatedly with successive notes, as it often does on a 4-or 8-voice synth, the slight difference in each voice (even in chords) will serve this illusion well.

NOISE

For adding grit and emulating the sound of dirty, decaying circuits, try adding a touch of noise modulation to the pitch, cutoff, volume, and/or waveform destinations on your synth. A little goes a long way if you’re aiming for subtlety. That said, adding gratuitous amounts of noise modulation can serve as a handy alternative to overdrive or distortion.

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