14_Subtractive_synthesis

Filtering

The basic idea of subtractive synthesis is similar to making coffee: something goes through a filter to remove unwanted components from the final product.

The .dumpClassSubtree message

Get a list of ugen filters in SuperCollider 3, by sending the .dumpClassSubtree message to the Filter class, as inFilter.dumpClassSubtree;

( Object.dumpClassSubtree prints all SuperCollider classes)

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• Filter - Base class for filter UGens
  • BEQSuite - Base class for B Equalization Suite
    • BAllPass - All Pass Filter
    • BBandPass - Band Pass Filter
    • BBandStop - Band reject filter
    • BHiPass - 12db/oct rolloff - 2nd order resonant Hi Pass Filter
    • BHiShelf - Hi Shelf
    • BLowPass - 12db/oct rolloff - 2nd order resonant Low Pass Filter
    • BLowShelf - Low Shelf
    • BPeakEQ - Parametric equalizer
  • BPF - 2nd order Butterworth bandpass filter.
    • BRF - 2nd order Butterworth band reject filter.
  • Changed - Triggers when a value changes
  • Decay - Exponential decay
  • Decay2 - Exponential decay
  • DetectSilence - Detect when input falls below an amplitude threshold
  • FOS - First order filter section.
  • Formlet - FOF-like filter.
  • FreeVerb - A reverb
  • Integrator - A leaky integrator.
  • LPF - 2nd order Butterworth lowpass filter
    • HPF - 2nd order Butterworth highpass filter.
  • LPZ1 - Two point average filter
    • HPZ1 - Two point difference filter
  • LPZ2 - Two zero fixed lowpass
    • BPZ2 - Two zero fixed midpass.
    • BRZ2 - Two zero fixed midcut.
    • HPZ2 - Two zero fixed midcut.
  • Lag - Exponential lag
    • Lag2 - Exponential lag
    • Lag3 - Exponential lag
    • Ramp - Break a continuous signal into line segments
  • LagUD - Exponential lag
    • Lag2UD - Exponential lag
    • Lag3UD - Exponential lag
  • LeakDC - Remove DC
  • Median - Median filter.
  • MidEQ - Parametric filter.
  • MoogFF - Moog VCF implementation, designed by Federico Fontana
  • OnePole - One pole filter.
    • OneZero - One zero filter.
  • RLPF - A resonant low pass filter.
    • RHPF - A resonant high pass filter.
  • Resonz - Resonant filter.
  • Ringz - Ringing filter.
  • SOS - Second order filter section (biquad).
  • Slew - Slew rate limiter.
  • Slope - Slope of signal
  • TwoPole - Two pole filter.
    • APF - FIXME: APF purpose.
    • TwoZero - Two zero filter.
  • VarLag - Variable shaped lag

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Use LPF, a low-pass filter to subtract high-frequency content from an input source.( SynthDef("subtractive", { arg out; Out.ar( out, LPF.ar( Pulse.ar(440, 0.5, 0.1), // the source to be filtered Line.kr(8000, 660, 6) // control the filter frequency with a line ) ) }).add; ) Synth("subtractive")

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RLPF, a resonant low-pass filter, removes high-frequency content and emphasizes the cutoff frequency.( SynthDef("passLowFreqs2", { arg out; Out.ar( out, RLPF.ar( Saw.ar([220, 221] + LFNoise0.kr(1, 100, 200), 0.2), [LFNoise0.kr(4, 600, 2400), LFNoise0.kr(3, 600, 2400)], 0.1 ) ) }).add; ) Synth("passLowFreqs2")

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Resonz is a very, very, very strong filter. Use it to emphasize a frequency band.

Transform noise into pitch with a sharp cutoff.( SynthDef("noiseToPitch", { arg out = 0, mul = 1; Out.ar( out, Resonz.ar( WhiteNoise.ar(mul), LFNoise0.kr(4, 110, 660), [0.005, 0.005] ) ) }).add; ) ( // activate left and right channels Synth("noiseToPitch", [\out, 0, \mul, 1]); Synth("noiseToPitch", [\out, 1, \mul, 1]); )

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