Expand your sound palette with oscillator morphing.
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The oscillators in early analog synthesizers could produce only a few simple waveforms, so the job of shaping the tone color was handled by filters. Today, digital oscillators are far more sophisticated. Filters are still incredibly useful, but you can produce many types of lively, animated sounds without resorting to them.

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FIG. 1: These settings for the SpectroMorph oscillator produce a very muted sawtooth sound (top) and a highpass-filter sound (bottom). The display is a graph of overtone amplitudes.

Among the most powerful of the new oscillators are those in u-he Zebra 2 ( This modular soft synth has a lot of slick options for timbral manipulation, but the highly flexible sound of the Zebra oscillators starts with waveform morphing. You can work directly with the waveshape or with the additive overtone spectrum.

Fake Filter Sweeps

Starting from Zebra's initial patch, choose SpectroMorph for the Oscillator mode. In this mode, the graphic display shows the waveform's overtone spectrum, not its waveshape. Set wave 1 to produce a very muted sawtooth tone, and set wave 16 to produce a very buzzy highpass sawtooth (see Fig. 1). While wave 16 is selected, Command-click (Mac) or Alt-click (Windows) on the wave 1 selector box to write new waveforms to tables 2 through 15 that morph smoothly from wave 1 to wave 16.

In the Oscillator module, assign Env2 as the modulation input for the wave parameter, turn up the amount, and turn envelope 2's sustain down to 0. When you play a note, you should hear a sound much like a highpass-to-lowpass filter sweep. You can control the sweep's length by adjusting envelope 2's decay time. By creating more-complex frequency spectra for the two end points of the morph, you can generate a variety of sweep colors. By editing individual wave spectra in the middle of the series, you can create colorful bumps in the sweep. After doing any edits, reselect wave 1 to make it the end point for the envelope sweep.

In GeoMorph mode, the oscillator display shows the actual waveform rather than the overtone spectrum. For classic pulse-width modulation, drag the waveform points to create a very narrow pulse shape in wave 1, create a square wave in wave 16, and, as before, set up a morph from one to the other.

Shimmering Bell Overtones

SpectroBlend mode provides pinpoint control over the overtones. Choose wave 1 and click on a few places in the display to create a waveform with some random overtones. Option-Command-click (Mac) or Ctrl-Alt-click (Windows) on the next seven waves to copy your spectrum to each of them, then edit each one very slightly.

Choose Lfo2 as the wave-modulation input, turn up the modulation amount to about 3.6, and slow down the rate of LFO2. Select wave 4 as the starting point because the LFO waveform goes both positive and negative. You'll hear subtle animation produced by the LFO sweeping slowly across the slightly different waveform spectra.

When you have something you like, Ctrl-click or right-click on the word Default in the Oscillator module and save your settings as an oscillator preset. Create a second oscillator, load this preset into it, slightly detune the two oscillators from one another, and pan them left and right. Increase the release time on envelope 1 and strike a few keys. You should hear a rich bell sound in which individual overtones fade in and out in subtle ways.

Wave Sequencing

To imitate PPG and Korg Wavestation-style wave sequencing, choose SpectroBlend mode and create 16 different waveforms with a lot of variety. Turn the Resolution knob all the way up to create sharper transitions between waves when step modulation is used.

Choose Lfo2 as the input for the oscillator's Wave modulation and turn up the amount to about 7. Set the LFO to the user waveshape, its Restart mode to gate, and its Sync value to ⅛. Leave the LFO waveshape display in Steps mode and draw some random steps. Now the LFO will produce a rhythmic wave sequence.

You can enhance the effect by switching to the oscillator's FX page and using another stepping LFO to modulate the Formanzilla or Ripples effect. Alternatively, use a wave-sequencing oscillator as an input for one of Zebra's FM oscillators or a comb filter. With a little experimentation and a modicum of taste, you can achieve spectacular results (see Web Clip 1).

Jim Aikin writes regularly for EM and Mix.