ES1 provides an attack, decay, sustain, and release (ADSR) envelope that can shape filter cutoff and the level of the sound over time.
Attack slider: Set the time it takes for the envelope to reach the initial desired level.
Decay slider: Set the time it takes for the envelope to fall to the sustain level, following the initial attack time.
Sustain slider: Set the sustain level, which is held until the key is released.
Release slider: Set the time it takes the envelope to fall from the sustain level to a level of 0.