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 control sets 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 control determines 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 control 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.

DECAY: This Control sets the Decay time of the EGR from 1 msec to 10 seconds.

SUSTAIN: This is a level control for the sustained part of the envelope.

RELEASE: This is the time for the envelope to return to zero, from 1 msec to 10 seconds.