Recently (as of this writing) a thread has been developing on the modular synthesizer forum Muff Wiggler discussing the “snappiness” of modular synthesizer Envelope Generators. That thread can be found at this link. Envelope Generators, or EGs, provide voltage controls for Attack, Decay, Sustain and Release which are used by other modules for a variety of functions.
Attack, Decay, Sustain, Release (or ADSR) envelopes can be understood by thinking of striking a piano key; The Attack is the time taken for the sound to go from zero to its peak volume. This is very fast on a piano as it occurs when the hammer hits the string. The Decay time is the time taken to go from the maximum volume to the Sustain volume. The Sustain level is the volume at which the note sounds while the key is held down. The Release time is the time taken for the note to decay to zero volume from the Sustain volume once the key has been released.
While this example is auditory these same properties can be applied to electronic envelopes used by synthesizers. Unlike a piano’s ADSR envelope where physics of motion are limited by, say, the vibratory properties of a piano string, electronic envelopes are far more flexible.
For a more detailed explanation of ADSR envelopes you can follow this link to Wikipedia.
It should be noted that other envelopes created by EGs can be Attack Release (AR), Attack Hold Decay Sustain Release (AHDSR) or Attack, Decay, Release (ADR) but it is not the purpose of this article to get that deep into the various envelope types.
In the aforementioned thread the discussion pertains to the ability of EGs provided by various manufacturers to execute these functions is a snappy or very timely manner. The extremely fast EGs can be used to create synthesized percussive sounds which have very fast Attack and rapid Release phases.
In order to illustrate the capabilities of some popular MU format Envelope Generators Lower West Side Studio prepared the following video.