User Guide

D. ENVELOPES
When we think of a musical sound, say a plucked string, we think of it as having a
start and an end. In the case of a plucked string, it begins with a burst of energy
and then slowly fades out until it is silent. In synthesis terms, this is called an envelope
– a shape that defines the changes that occur in a sound over time. An envelope
can define any aspect of a change in sound – volume, timbre, or pitch for
example. The Voyager has two envelope generators. When triggered, these circuits
produce control voltages that vary as determined by the attack, decay, sustain and
release controls. The Attack control determines the character of the onset of the
sound. A short attack time corresponds to a sudden sound like a percussion
instrument or a plucked string. A long attack time corresponds to a gradual onset of
sound like a plane flying overhead, or the slow crescendo of a bowed string
instrument. The Decay is the second stage in the evolution of a sound before it
sustains or dies out. For instance with a plucked string – the sound begins with a
burst of energy which begins quickly, then drops back to a lesser level of energy
and then proceeds to fade out from there. The decay is the time that it takes for the
signal to drop down to the level set by the Sustain control. The decay time has no
effect when the sustain level is set at 10. As long as a key is held down, the note will
sustain at the sustain level. After the key is released, the Release time determines
how long it takes for the sound to fade out. An envelope can be used to describe
the shape of the volume of a sound, it can also be used to describe other aspects
of sound – say timbre or pitch. An envelope is used to generate the evolution of the
sound after the note begins.
The Voyager has two envelope generators, one for modulating the filter, and
one for modulating amplitude. The envelopes can also be used as Modulation
sources or Modulation shaping for other parameters through the Mod Busses.
ATTACK:
This control sets the Attack time of the EGR from 1 msec to 10 seconds.