# Faust: A Simple Envelope

Temporal envelopes are essential for many sound synthesis applications. Often, triggered envelopes are used, which can be started by a single trigger value. Faust offers a selection of useful envelopes in the envelopes library. The following example uses an attack-release envelope with exponential trajectories which can be handy for plucked sounds. The output of the sinusoid with fixed frequency is simply multiplied with the en.arfe() function.

Check the envelopes in the library list for more information and other envelopes:

https://faust.grame.fr/doc/libraries/#en.asr

// envelope.dsp
//
// A fixed frequency sine with
// a trigger and controllable release time.
//
// - mono (left channel only)
//
// Henrik von Coler
// 2020-05-07

import("stdfaust.lib");

// a simple trigger button
trigger  = button("Trigger");

// a slider for the release time
release  = hslider("Decay",0.5,0.01,5,0.01);

// generate a single sine and apply the arfe envelope
// the attack time is set to 0.01
process = os.osc(666) * 0.77 * en.arfe(0.01, release, 0,trigger) : _ ;