Self-Oscillation Is Key
We’ve already touched on the value of FX that can be utilised in any project. Noise generators are one way of producing such patches, but there is another option. Some synths include filters that are capable of self-oscillating – the filter can produce a resonance setting so high that it becomes a sound source in its own right. A self-oscillating filter can actually supply 100% of the sound in a patch. Oscillators can be removed or disengaged. Although the sound is not atonal (as we saw with white noise), when modulated it can generally be placed in any project regardless of pitch. Classic laser FX, resonant ‘zaps’, whistling sweeps and acidic squelches are the order of the day here. These resonant sound sources are perfect for sculpting FX patches and can cut through the busiest mix.
First, check that your synth is capable of self-oscillation. Some synths have a physical switch to allow self-oscillation and others have a specific filter mode. If there is no clear indication that your synth supports self-oscillation, you can perform a simple experiment. Push the resonance all the way to the top then turn off all the oscillators you can. Now when you sweep the cutoff frequency you should hear your new sound source.
Once you have identified an instrument that is suitable, you can treat the filter more or less like an oscillator. Try modulating the cutoff with LFOs or envelopes; mapping the cutoff to a physical control like your mod wheel can also work very well. Try keeping sustain settings high and combining your self-resonating patches with reverb to create eerie soundscapes. On the flip side, short decay based filters will produce sharp zaps and percussive FX – good for accentuating key parts of a drum pattern.
If your filter section has a drive or distortion, you can use it to introduce more complex harmonics into the sound. For further complexity you can even mix oscillators or noise back into the patch.