ARP 2600 - Using Lag Processor for Control Voltages

95
5.4 SOUND
EFFECTS.
Here is a
place to
put patches
that specifically
imitate
natural
sounds. If
you
wish
to put
musical-instrument
sounds
in
here,
you might
make
a separate
sub-classification.
PWN
(Pulse Width
Modulation
I.
In general,
control
settings
for any
imitations of
natural sounds
will
be
quite
critical.
In
this
case, begin with
the VCF wide open
and tune
the
VCO to
an initial frequency
and
pulse-width
setting that
catches
what feels
like
the right
tempo
for footsteps
.
Then
retune this
by
adding
a
small amount
of noise
modulation
to
the
pulse-width,
closing the
VCF
perhaps
a
little
way,
adjusting
perhaps the color
of
the
noise,
and adding
at
a
low stepping
rate a little FM from
the
S/H circuit.
This last step
is a
kina
of super-
refinement;
it
produces slight
irregularities in
the
speed
of
the
footsteps.
If,
finally,
you add a little
of
the
S/H output
into the
VCF control,
you
will get
the effect of walking
over different
Kinds
of
material
or
in-different
acoustic
surroundings as
the
S/H
voltage changes,
by small
amounts, the Fc
ot
the filter.