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OB-6 Operation Manual
Loudness Envelope
Loudness Envelope
After passing through the filters, a synthesized sound goes into an analog
voltage controlled amplifier or VCA, which controls its overall loudness.
The VCA has a dedicated, four-stage envelope generator.
The Loudness Envelope is used to shape the volume characteristics of
a sound over time by giving you control over its attack, decay, sustain,
and release stages. Along with the filter envelope, this is one of the most
important factors in designing a sound.
Without a loudness envelope, the volume of a sound wouldn’t change
over the duration of a note. It would begin immediately, remain at its full
volume for the duration of the note, then end immediately when the note
was released. Again, that’s not very interesting sonically and it’s not typi-
cally how instruments behave in the real world.
To give you a real-world example, the main difference between the
sound of the wind and the sound of a snare drum is that they have very
different loudness envelopes. Otherwise, they are essentially both white
noise. Wind has a relatively slow attack, a long sustain, and a long decay
and release. A snare drum has a sharp attack, no sustain, and virtually no
decay or release. But again, they are both fundamentally white noise.
LOUDNESS ENVELOPE
ATTACK
DECAY
SUSTAIN
RELEASE
AMOUNT
VELOCITY
Loudness Envelope
Attack
Decay
Sustain
Release
Amplitude
Time
A typical four-stage, ADSR envelope shape
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