En v e l o p e 2: V C A
The volume of the audio signal, which passes
through the VCA envelope, is contoured by the
envelope controls. Each time a key is pressed,
the envelope or "contour" generator attached
to the amplifier is actuated, and sends a control
signal to the amplifier. Like the filter envelope
control signal, the VCA envelope control signal is
composed of the same four segments: initial rise,
decay, sustain level, and release time. The
volume of the note is shaped according to the
settings of the envelope controls. These four parameters are shown below.
Selects the attack time. The attack time determines the duration of the initial rise
in volume to a peak. Notice the sound take on different qualities as you increase
from a short sharp attack to a long slow crescendo.
Selects the decay time. The decay time determines the duration of the drop in
volume from the initial peak to the sustain level. Shorter decay times will produce
more percussive sounds; the longer times will begin to "open" up the sound.
Selects the sustain level. The sustain level determines the volume level at which
the envelope contour levels off after the attack and decay. Set at
0
0, no sustain
level is heard. Set at
50
50, the contour diminishes to a low volume. Set at
127
127, no
drop in volume is heard after the initial peak is reached.
Selects the release time. The release allows the sound to fade out at the time set,
rather than immediately upon release of a note or key. This "final decay" takes
effect after the sustain level segment of the envelope.
ENVELOPES
continued (still) on next page.
