Subtractive: Faust Examples

VCO-VCA-VCF

The first example for subtractive synthesis implements a virtual chain of VCO, VCF and VCA, as shown in the Faust diagram in [Fig.1].

/images/Sound_Synthesis/subtractive/process_subtractive_1.svg

[Fig.1]

Faust diagram for the VCO-VCA-VCF example.

The three modules are definied as individual functions, with paramters controlled by horizontal sliders. In the processing function, they are chained using the : operator.

A resonant low pass from the filters.lib - the Faust Filters library - is used.

// sawtooth-filter.dsp
//
// First steps with a VCO-VCA-VCF setup.
// The three modules are connected in series.
//
// No anti-aliasing!
//
// - steady sound
// - control over f0, cutoff, resonance, gain
//
// Henrik von Coler
// 2020-05-17

import("stdfaust.lib");

//////////////////////////////////////////////////////////////////////////
// Control Parameters
//////////////////////////////////////////////////////////////////////////

cutoff      = hslider("Cutoff", 100, 5, 6000, 0.001):si.smoo;
f0          = hslider("Pitch", 100, 5, 16000, 0.001):si.smoo;
q           = hslider("Q", 1, 0.1, 5, 0.01):si.smoo;
gain        = hslider("Gain", 1, 0, 1, 0.01):si.smoo;

//////////////////////////////////////////////////////////////////////////
// Define three 'module' functions
//////////////////////////////////////////////////////////////////////////

vco        = os.sawtooth(f0);
vcf         = fi.resonlp(cutoff,q,1) ;
vca(x)    = gain * x;

//////////////////////////////////////////////////////////////////////////
// Define three 'modules'
//////////////////////////////////////////////////////////////////////////

voice =  vco  : vcf : vca;

process = voice  <: _,_ ;

Triggered

The example subtractive_triggered.dsp from the repository extends the previous sawtooth example with temporal envelopes for VCF and VCA and implements four voices with individual control. The block diagram is shown in [Fig.2].

/images/Sound_Synthesis/subtractive/process_subtractive_2.svg

[Fig.2]

Faust diagram for the triggered subtractive example.

The example makes use of the Moog filter from the vaeffects.lib library of virtual analog filter effects.
Individual control over the voices is realized through the % command within the voice() function.

// subtractive_triggered.dsp
//
// A four voice subtractive synth.
//
// - trigger
// - control over f0, cutoff, resonance, gain
//
// Henrik von Coler
// 2020-05-17

import("stdfaust.lib");

trigger0 =  button("trigger0 [midi:key 33]");
trigger1=  button("trigger1 [midi:key 34]");
trigger2=  button("trigger2 [midi:key 35]");
trigger3=  button("trigger3 [midi:key 36]");

//////////////////////////////////////////////////////////////////////////
// Define three 'module' functions
//////////////////////////////////////////////////////////////////////////

vco(f0)          = os.sawtooth(f0);
vcf(c,r)          = ve.moog_vcf(r,c);
vca(x,gain)    = gain * x;


//////////////////////////////////////////////////////////////////////////
// A function with envelopes
//////////////////////////////////////////////////////////////////////////

voice(index,trig) =  vco(f0) : vcf(fc,res) : vca(env1) * 0.5
with
{
// use an individual hslider for every
f0                = hslider("Pitch %index", 100, 5, 1000, 0.001):si.smoo;

//trig = button("trigger%index");

rel1 = hslider("rel_vca%index", 0.5, 0.01, 3, 0.01):si.smoo;
rel2 = hslider("rel_vcf%index", 0.25, 0.01, 3, 0.01):si.smoo;

env1 = en.arfe(0.02, rel1, 0,trig); // en.adsre(0.001,0.3,1,1,trig);
env2 = en.arfe(0.01, rel2, 0,trig); //en.adsre(0.001,0.3,1,1,trig);

cutoff = hslider("cutoff%index", 100, 5, 6000, 0.001):si.smoo;
res     = hslider("res%index", 0.1, 0, 1, 0.01):si.smoo;

fc         = 10+env2* cutoff;

};

process = voice(0,trigger0),voice(1,trigger1),voice(2,trigger2),voice(3,trigger3) :> _,_ ;