ADSR Â Schematic of #ADSRÂ
The most common kind of envelope generator has four stages: attack, decay, sustain, and release (ADSR).[3] #envelopegenerator  Attack is the time taken for initial run-up of level from nil to peak, beginning when the key is pressed. Decay is the time taken for the subsequent run down from the attack level to the designated sustain level.Â
Sustain is the level during the main sequence of the sound's duration, until the key is released. Release is the time taken for the level to decay from the sustain level to zero after the key is released.[4] While, attack, decay, and release refer to time, sustain refers to level.[3] Â The Hammond Novachord in 1938 uses an early implementation of an ADSR envelope. A seven-position rotary knob set preset ADS parameter for all 72 notes; a pedal controls the release.[1] Â
The envelope generator was created by the American engineer Robert Moog in the 1960s. While experimenting with the first Moog synthesizers, composer Herbert Deutsch suggested Moog find a way to articulate the instrument so notes did not simply trigger on and off. Moog wired a doorbell button to the synthesizer and used a capacitor to store and slowly release voltage produced from hitting a key. He refined the design to remove the need to push a separate button with every key press, with two switches on every key: one to produce the control voltage and the other to trigger the envelope generator.[2]Â
The envelope generator became a standard feature of synthesizers.[2] Â Following discussions with engineer and composer Vladimir Ussachevsky (then head of the Columbia-Princeton Electronic Music Center) in 1965, Moog developed a new envelope module whose functions were described in f T1 (attack time), T2 (initial decay time), ESUS (sustain level), and T3 (final decay time). These were later simplified to the modern ADSR form (Attack time, Decay time, Sustain level, Release time) by ARP.[2] In sound and music, an envelope describes how a sound changes over time. It may to relate to elements such as amplitude (volume), filters (frequencies) or pitch.[citation needed] For example, a piano key, when struck and held, creates a near-immediate initial sound which gradually decreases in volume to zero. Â
Envelope generators, which allow users to control the different stages of a sound, are common features of synthesizers, samplers, and other electronic musical instruments. The most common form of envelope generator is controlled with four parameters: attack, decay, sustain and release (ADSR). weki