The ADSR model (Attack, Decay, Sustain, Release) is a sound synthesis technique based on parameters that influence the sound. In this method, the sound frequencies are decomposed into time- and amplitude-dependent factors.
In the ADSR model, the rise times of sound images and the maximum amplitude values are determined, as well as the fall times in which the sound drops in amplitude, in addition to the hold time, which is the time during which the amplitude changes only slightly, and the decay time, during which the amplitude falls back to zero.
ADSR is generated in corresponding generators, which are also called envelope generators. With such an ADSR generator, the volume can be determined in the time from the attack, through the decay and sustain , to the release. The individual time sequences can be varied as desired.