Technical data
EXERCISE
9:
MODIFYING
NOISE
WITH
THE
FILTER
SECTION
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1.
Hold
down
any
key
on
the keyboard.
The
sound
source
is
the
NOISE
section.
2.
Slowly
rotate
the
CUTOFF
control
counterclockwise.
The
highs
are
progressively
"cut
off."
(END
EXERCISE)
3.
Set
the
EMPHASIS
control
to
"10."
Now
move
the
CUTOFF
control
throughout
its
positions.
You
should
hear
"wind"
sounds
varying
pitch.
Noise
doesn't
have
harmonics
that
can
be
picked out
as
the
cutoff
frequency
is
moved.
The
FILTER
section
modifies
noise
just
as
it
modifies
any signal—by
cutting
off
the
highs.
The
preceding
Exercise
illustrates
not
only
how
the
FILTER
section
works,
but the
"smooth"
distribution
of
frequencies
in
noise.
Even
when
EMPHASIS
is
high,
no
distinctive
harmonics
are
heard
in
noise.
But,
at
high
EMPHASIS
control
settings
noise
will
begin
to
take
on
a
"pitch"
determined
by
the
cutoff
frequency.
This
is
because
only
that
portion
of
noise
around
the
cutoff
frequency
is
emphasized,
making
it
easier
to
hear.
CONTROLLERS
A
controller
generates
a
signal
that
is
used
to
control
modifiers
and/or
sound
sources.
On
the
Multimoog,
controllers
may
be
used
to
alter
oscillator
frequency
and
waveshape,
filter
cutoff
frequency,
and
amplifier
gain.
Control
signals
are
not
heard
directly,
but
are
used
to
control
sections
that
generate
or
modify
sound.
To
return
to
our
discussion
of
sound,
this
means
we
can
control
pitch,
timbre,
and
loudness
with
a
voltage
level.
When
a
circuit
is
connected
to
the
control
input
of
a
section
of
the
Multimoog,
that
circuit
is
defined
as
a
controller.
From
experience,
you
know
that
the
keyboard
can
control
the
pitch
of
the
oscillator
section;
here
is
how
it
does
it.
The
keyboard
circuitry
produces
a
voltage
level
that
increases
as
you
play
up
the keyboard.
The
keyboard
is
connected
to
the
frequency
control
input
of
the
oscillator
section
by
placing
the
OSCILLATORS
switch
to
the
NORM
position.
Since
the
oscillator
section
is
voltage
controlled
(VCO),
an
increase
in
voltage
from
the
keyboard
causes
an
increase
of
oscillator
frequency.
When
you
play
up
the keyboard,
oscillator
pitch
goes
higher.
Other
controllers
on
the
Multimoog
include
the
FILTER
CONTOUR
section,
LOUDNESS
CONTOUR
section;
modulation
oscillator
and
sample-and-hold
circuits
selected
by
the
MODULATION
section.
In
some
cases,
the
OSCILLATOR
B
section
may
be
used
as
a
controller.
Control
signals
from
the
outside
world
may
also
be
routed
to
the
OSCILLATOR
A&B
and
FILTER
sections
via
the
OSC
A&B
and
FILTER
INPUTS
on
the
Multimoog's
rear
panel
(see
OPEN
SYSTEM
section
of
the
manual).
The
PITCH
ribbon
is
a
performance
controller
because
its
voltage
output
is
directly
under
the
control
of
the
performer.
Often
this
is
the
case
with
the
KEYBOARD
TOUCH
section
as
well.
KEYBOARD
The
keyboard
of
the
Multimoog
produces
a
voltage
level
that
may
be
used
to
control
the
frequency
of
the
oscillators
and/or
the
cutoff
frequency
of
the
FILTER
section.
The
following
Exercise
shows
how
the
keyboard
may
be
used
as
a
controller:
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