# FM Synthesis: Faust Example

The following Faust example is a triggered two-operator FM synth. Both operator frequencies and the modulation index can be adjusted through sliders. Global amplitude and modulation index have individual temporal envelopes with adjustable release times.

// fm-simple.dsp
//
// 2-operator FM synthesis
//
// - with trigger
// - dynamic modulation index
//   through temporal envelope
//
// Henrik von Coler
// 2020-05-11

import("stdfaust.lib");

/////////////////////////////////////////////////////////
// UI ELEMENTS
/////////////////////////////////////////////////////////

trigger  = button("Trigger");

f_1      = hslider("OP 1 Frequency",100,0.01,1000,0.1);
f_2      = hslider("OP 2 Frequency",100,0.01,1000,0.1);
ind_1    = hslider("Modulation Index",0,0,1000,0.1);

// a slider for the first release time
r1  = hslider("Release 1",0.5,0.01,5,0.01);

// a slider for the second release time
r2  = hslider("Release 2",0.5,0.01,5,0.01);

/////////////////////////////////////////////////////////
// FM Function
/////////////////////////////////////////////////////////

am(f1, f2, t1, r1, r2) = gain * os.osc(f1 + (os.osc(f2) * ind_1)* index1)
with
{
gain   = en.arfe(0.01, r2, 0,t1);
index1 = en.arfe(0.01, r1, 0,t1);
};

/////////////////////////////////////////////////////////
// processing
/////////////////////////////////////////////////////////

process =  am(f_1,f_2, trigger, r1 ,r2) <: _,_;