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TWO
VCO'S
IN
COMBINATION
A
large variety
of
sounds
is
possible
when
the outputs of both
VCO's
are
combined
1.
THE
SAME WAVEFORM
IN
THE SAME
RANGE
Usually
the
same waveforms
in
the
same
ranges
(as
shown
below)
are
used
for
two
note
chords.
For
the
one
note performance,
the
sound
becomes
rich
and
soft
with
a
chorus
effect
caused
by
the
slight
differences
in
pitch
of the
two
VCO's.
In
both
cases
it
is.
recommended
to
set
the
balance
at
equal
levels
with the
AUDIO
MIXER.
Set
the
SYNC
switch
at
OFF
except
for special
purposes.
Only
one
note
will
sound
even
when
two
notes are played
if
this
switch
is
on.
2.
THE
SAME
WAVEFORM
IN
DIFFERENT
RANGES
The
figure
below shows
the
combination
of
the
triangular
waveforms
of
8'
and
2',
which
can be used to produce
the
sound
of
a vibra-
phone,
for
example.
This
combination
is
very
useful.
It
is
often
used
for
making
organ-like
sounds,
for
example. For
this
purpose, the
combination
of
2
2/3'
or
1
1/3'
will
be
effective.
These can be obtained by
tuning
VCO-2
a
perfect
fifth
above
VCO-1
with
the
VCO-2
TUNING
control.
Large
sounds can be
obtained with combinations
of the various square
wave
(as
explained
in
the
description of
VCO-1
(A)) as well as the
sawtooth
waveform.
The
correct
adjustment
of the
AUDIO MIXER
controls
is
very
important
since
the
sound
wiii
vary
greatly
with
different balances.
3.
DIFFERENT
WAVEFORMS
IN
DIFFERENT
RANGES
Among
combinations
of
this
kind,
the
most
useful
is
to
combine
a
sawtooth
or square
wave
with
a
triangle
wave
of a
different range.
The
8'
sawtooth
is
added
to the 16' triangular
waveform
in
the
figure
below;
the
tone
color of
the
sawtooth wave
is
retained
but the
sound
becomes
heavier
with the
intensified bass.
Adding
a
higher range
sound
of
2'
or
4'
can
produce
special
tone
colors.
In
addition,
com-
bination of
sounds
of
two
or three octaves
distant
such
as
8'
and
32' or
4'
and
32'
is
effective.
PULSE WIDTH
—
WAVEFORMS AND
HARMONICS
All
waveforms
except
the sine
wave
can be generated
by
a
combination
of a
fundamental
sine
wave
of the
pitch
frequency
and
a
group
of
sine
waves which
are
multiples of the
fundamental;
therefore,
any
waveform
can be
synthesized
by combining
a
fundamental
sine
waveform
with
a
proper
ratio
of
harmonics.
The
drawing below shows
a
fundamental
with
its
harmonics.
The
white
notes
are
even
numbered
harmonics and
the black notes are
odd num-
bered harmonics. (True harmonics
are actually
slightly
different
from
the pitches
produced by
the equally
tempered
scale.) All
waveforms,
except
the
sine
wave, contain harmonics.
It
is
this
harmonic
content
that gives
each
sound
its
particular
tone
color.
b-0-
*-
v
-o-
FUNDAMENTAL
2ND
3RD
4TH
5TH
6TH
8'
4'
2-2/3'
2'
1-2/3'
1-1/3'
7TH
8TH
HARMONIC
V
11
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