Sunday, August 28, 2011

Technique: How to make that dubstep formant bass

There are several ways and variations on how to create formant sounds (ie. human vowel sounds) with synthesizers. Today I'll concentrate on one of them: filtering + sample rate reduction.

The theory goes that when the audio frequencies hit the Nyquist Frequency (samplerate/2) the higher frequencies start bouncing/mirroring back to the lower frequencies. This causes the harmonics to modulate each other as some of them are moving up and some are moving down at the same time. You can use this phenomenon to create formant sounds. First make sure your samplerate is really low, like maybe 6kHz or so (try different settings in sample reduction plugin/hardware). Then sweep your audio source from low to high frequencies and see what happens. You should hear something resembling formants going like "ayyayyyayyy!" as made famous by Skrillex and others in the dubstep community.

It's best to use simple sounds which you run through sample rate reduction. This usually gives the best results. Try a simple oscillator + lowpass/bandpass filter with resonance cranked high. When you move the filter cutoff, you should hear clear formants coming out of your speakers. You can also try changing the sample rate while you're changing the filter cutoff. This gives you even more wide range of interesting and usable sounds.

If the sample rate is stable, you'll hear metallic hissing kind of artifacts in your sound. If you don't want this in your sound, you can reduce the effect by modulating the sample rate with noise ever so slightly.

So to recap what's been told so far, here's the signal flow:

Oscillator --> Filter(lowpass/bandpass with resonance) --> SampleRateReduction --> Speakers

You should note that reducing sample rate has a destructive effect on the lower frequencies also. Because of this it might be a good idea to highpass filter the formant sound and layer it with sub bass. This will give you best of the both worlds: crispy formant action + clear and powerful low end.

The above is exactly what I've done in my latest song. Here's a short clip of the bass synth soloed:

Alternative content

As you can hear, the formant bass is frequently switched between a non formant bass sound. The main difference between the sounds is that the non-formant bass hasn't been ran through the sample rate reduction. Just to give you an idea how the non-formant bass sounds on its own, here's a clip of it:

Alternative content

If you're interested in hearing what the above bass sounds in the context of the finished track, you should listen to this:

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