Sequential prophet 5 - Page 18

RESONANCE
knob;
Adjusts
the
amount
of
filter
resonance.
As the setting is increased
from
to
approximately
7
the
amount
of
resonance
("emphasis," "regneration," or
"Q")
applied
to
those
signal
components
at
the
cutoff
frequency
will increase.
As
resonance
increases,
frequencies
lower
than
the
cutoff will
become
decreasingly
audible in
comparison
with
those
nearer
the
cutoff.
As the
knob setting is
increased
beyond
7,
the
filter
breaks
into
oscillation,
acting
like
a sine-wave audio source
whose pitch is
determined
by
the
cutoff
frequency.
ENVELOPE
AMOUNT
knob;
The
filter
cutoff may
be contoured
(shaped)
electronically
according
to
a
voltage
pattern
provided by
the envelope generator. The
specific
envelope
is
shaped
by
the
ATTACK,
DECAY,
SUSTAIN, and
RELEASE
(ADSR)
knobs.
The
ENVELOPE
AMOUNT
knob is
an attenuator
which sets the depth of
the
applied
envelope.
Creating
the
envelope
itself with the
ADSR
knobs is discussed below.
KEYBOARD
switch;
When
on, the
KEYBOARD
control
voltage (CV) is
applied to
the
filter's
cutoff
frequency
just
as it
is
normally applied
to OSC
A and optionally
applied
to
OSC
B.
With
the
filter thus
"tracking" the
keyboard, its
cuttoff
frequency
is
maintained at
a
constant
point relative
to the
notes
being played.
This
results in
a
consistency
of
timbre
over the
whole
keyboard
range. When
FILTER KEYBOARD
is
switched
off, notes
played
higher on
the
keyboard
will have more
of their
overtones
suppressed
than notes
played
lower.
As a
result, the
higher
notes will have
a
duller
timbre.
If
FILTER
RESONANCE
is set
for
self-oscillation
(e.
g.
above
7),
then switching
FILTER
KEYBOARD on
will
allow the
filter
to
be
played from
the keyboard. Unless a
complex
effect is
desired,
the
FILTER
ENVELOPE
AMOUNT knob will
in
this case
normally be set to
(to
maintain a
steady response
from voice to voice).
LEVEL
ENVELOPE
AMOUNT
(fTlLTER ONLY)
TIME
LENGTH
OF TIME THAT
KEY IS HELD DOWN
Figure
2-5
ENVELOPE
The filter envelope generator contours timbre
by
controlling the
filter cutoff
frequency. The
contour pattern
is
initiated when
a
key
is
struck,
producing a
gate.
The
initial
appearance of the gate "triggers" the envelope generator(s) to
proceed
through
their attack
and decay periods. After the attack and decay
periods
set for
each
envelope
generator
have elapsed,
the
generator will
produce a
steady
control voltage
(CV) at the
level set by the
SUSTAIN knob for
as
long
as
the
GATE
is
present
(indicating the
key
is
held). When
the key
is released, the
GATE
goes off and
the
envelope
generator
output voltage drops to zero at a rate
set by the
RELEASE knob.
CMIOOOD
2/82
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