57
(You will
notice,
while
you
are doing this, that the filter
does
not completely
cut off frequencies below
its peaking
frequency.
Remem-
ber
that it is
after
all a low-pass
filter,
and increasing its resonance
so
that
h peaks
at F
c
may attenuate lower frequencies considerably
but
will not
cut
them off. If
it did it would
be a
bandpass
filter.)
Initial
I
jJtex
Frequency
4WOVNUY
*
&/*&?&&*&*/*.'*
-
out
When you
have reached
the extreme
right
position of the filter
initial frequency
control, the peak
in
the filter's
output will have
passed
pretty much
beyond audibility,
and
the
audible output will
be
simply
a
much attenuated version
of
the VC03 sawtooth input.
Lower-
ing
the filter
resonance to minimum will restore
this to
its
original
level.
It
will
also,
of course, remove
the peak from the
filter output,
as
you will discover
if, having lowered the
resonance control
to
mini-
mum,
you
sweep the initial filter frequency
back from right
to
left.
The upper
harmonics will drop
ou: but without being individually
em-
phasized
by any
peak
in the filter
response. It
becomes
in
fact
extremely
difficult
to
hear any of the upper harmonics
individually;
they
all
seem
to
combine
to produce a general
sense
of the timbre of
the tone
you
are hearing.
And
varying
the filter F
c
seems
only
to
change
this
timbre
from bright
to dull
or
somewhere in
between.
Since the resonance control
is continuously variable,
it
can
give
any
desired
degree
of
peaking short of the
extremely
sharp
peak
you
have
just
used. For musical
purposes
these
intermediate positions
are
most useful;
in conjunction with
the variable
F
c
of
the filter, they
give you
an
enormous amount of control over
the timbre of the
musical
tones
you
wish to
produce.
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