The Kyma Language for Sound Design, Version 4.5

Distortion
Waveshaping
Clipping
By applying some nonlinear processing to your Sounds, you can add extra harmonics to the output,
making it spectrally richer. This is the technique behind things like frequency modulation, ring modulation,
waveshaping, and even cranking your guitar amp beyond the range where it has a linear response
— all in an effort to broaden the spectrum and avoid those pure, yet boring, sine waves.
The key to producing distortion in a signal is to process it in a nonlinear way. Demonstrate this to yourself
right now by opening up WS distortion. A Waveshaper uses the value of its Input as the index into the
wavetable named in ShapingFunction.
Try out a linear shaping function by setting the ShapingFunction parameter to FullRamp. FullRamp
is a straight line from -1 up to 1. To see FullRamp, hold down the Command or Control key and click
the disk button next to the ShapingFunction field; FullRamp looks like a straight line. Now select WS
distortion, and choose Oscilloscope from the Info menu. Use a MIDI keyboard to play the harp sample
and look at the waveform.
Next, try changing the ShapingFunction to WinSine4. Hold down the Command or Control key and
click the disk button in order to see what the WinSine4 wavetable looks like; this is definitely not a
straight line. Then select WS distortion and choose Oscilloscope from the Info menu. Play some low
notes on the MIDI keyboard and look at the difference in the shape of the waveform being displayed on
the oscilloscope.
Waveshapers are not the only way to apply a nonlinear process to a signal. One really simple way is to
simply turn it up too loud. This clips the signal, and introduces sharp edges (and thus new harmonics) in
the waveform where before there were only smooth curves.
Take a look at sub-fundamental distortion. Notice that your sound here is fed into a Gain and that the
Gain is set to 10. Select the Gain, choose Oscilloscope from the Info menu, and watch what happens to
the shape of the waveform as you increase the !Volume fader. This clipped signal is fed into LPF which
filters out all but the lowest frequencies. Try playing sub-fundamental distortion and adjusting !Volume.
For complex signals, clipping introduces distortion products that are below the fundamental as well as
above the fundamental of the signal.
Frequency Modulation
The reason that frequency modulation (FM) can be used to synthesize complex tones is that it, too, is a
nonlinear process and adds extra harmonics where there were none before. In Kyma, you can use any
Sound as an FM modulator, including samples or the live input. Try playing Harp FM; this uses a Celtic
harp sample as the modulator on a sine wave oscillator. The higher the modulation index, the more harmonic
distortion is introduced.
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