Yamaha CS-80 Instruction Manual page 44

SECTION
V - UNDERSTANDING SYNTHESISERS
4
i
40 This section
first
deals with
several basic conceptual
questions
about
synthesizers. While
we
have
distilled
the information
as
much
as possible,
some
topics have
philosophical or
complex
origins that
do not
lend
them-
selves to simple explanations.
The
balance of the section
provides an overview
of
how
the
CS-80
operates,
much
of
which
can
also
apply
to
other
synthesizers.
What
is
a
Synthesizer
A
synthesizer
is
an audio processor that has
a built-
in
sound
generator
(oscillator),
and
that
alters
the
envelope of the sound with
voltage controlled
circuitry.
Synthesizers can produce
familiar sounds and
serve
as musical instruments,
or
they can
create
many
unique
sounds and
effects of their
own. The
synthesizer oper-
ates
by
creating each
basic
element
of
sound and
then
providing you with separate controls
for
each element.
You
don't have
to use
all
the
many
controls
on
the synthesizer
to create
a
complete sound.
In fact,
often only
a
handful
of
the
available controls need
be
used, depending on
the
sound you
wish
to achieve.
The
Difference
Between
Synthesizers
&
Electric
Organs
An
electric organ offers
a
wide
variety of preset
sounds
at
the touch
of a finger. Synthesizers usually
offer
no
presets,
or very few
of
them,
instead pro-
viding an
infinite variety of adjustable sounds. The
CS-50, CS-60 and CS-80
offer
many
presets
and
infinitely adjustable sounds
as well.
Organs
utilize
different
means
to generate
sound
than do
synthesizers. Because
of
this,
most
organs
are
polyphonic,
meaning
that
you
can play
many
notes
simultaneously, whereas most
conventional
synthesizers
allow
you
to play only one
note
at a time.
The
CS-
Synthesizers, however, incorporate
additional
circuitry
that allows
you
to play
several notes
at a
time
(4
on
the
CS-50 and
8 on
the
CS-60 and
CS-80).
Why
Use
a
Synthesizer
Many
of
the sounds
that can be created with
a
synthesizer
would
be either Impossible
or highly
impractical to create
with acoustic instruments.
Also,
the synthesizer
can give
you
common
acoustical
sounds with
much
greater convenience
than
would
otherwise be
possible.
For
instance,
you
can adjust
the controls to "stretch"
a
common
instrument,
like
gradually transforming
a
piccolo to
a
Bass
flute, or
even
to a
20' long
flute.
If
there were such
a
thing.
Similarly, the synthesizer allows
Instant or gradual
transitions
from
the
sound
of
one instrument
to
another.
The
Elements
of
a
Synthesizer
One
section, the
VCO,
establishes the pitch or
frequency
of the note,
as well
as
the basic
tone
(timbre).
Another
section,
the
VCF,
shapes the tone
or
emphasizes portions of
it.
Another
section, the
VGA,
affects the
loudness
of the notes. Either the
VCF,
the
VCA,
or
both
may
be used
to
"turn on" and "turn
off" the sound
in a
controlled
pattern,
forming
the
notes
as
you
play the keyboard. The
control that
forms
the notes
is
provided by Envelope Generators
(EG), one
for
the
VCA
and one
for the
VCF. The
synthesizer
also
houses
many
other functions to
modify
the basic
sounds
for
a
variety of effects.
Yamaha
CS-series synthesizers,
because they are
polyphonic,
are
actually equipped
with several
VCO's,
VCF's, VGA's and
EC's: 16
sets
on
the
GS-80
for
creating each of the 8 notes times 2 voices that
can
be
played simultaneously.
Why
Voltage Controlled
Circuits are
used
in
Synthesizers
& How
They Work
You
can
set
up
voltage controlled
circuits to
make
changes
automatically. Suppose you have
a
sub
oscillator that produces
a
continuously changing
voltage (AG), such
as the
slow
sine
wave from
the
CS-80's
Sub
Oscillator.
If
you
apply that voltage to
the control input of
a
Voltage Controlled
Amplifier,
the
sound
passing through that amplifier
will
go
up
and
down
in
level— creating
a
tremolo
effect.
(This
is
exactly
what happens when
you
move down
the
VCA
lever In
the
Sub
OscillatorSection.)
At
this
point you
are listening to
one sound
source
that
is
being
modulated
or controlled by something
else, a
sine
wave.
If
you
Increase the
SPEED
of the
Sub
Oscillator, the rapid changes
in
control voltage
will
make
the sound
level
change
so
fast
that beating occurs,
producing secondary
tones.
You
can also adjust
a
voltage controlled
circuit
manually.
If
you
wish,
just like
any conventionally
controlled
circuit.
For example, you might
achieve the
same
slow-speed tremolo
effect
by continuously mov-
ing
a
Volume
control
up and down,
If
you
had the
fingers free to
do
it.
However, you
could not
possibly
move
that
volume
control
fast
enough
or
smoothly
enough
by
hand
to
produce secondary
tones.
Thus,
voltage controlled
circuits
enable you
to
do
things
that could not be
readily
accomplished
with purely
manually
controlled
circuits.
Amplifiers (VGA's)
are not the only voltage con-
trolled circuits in a synthesizer;
filters
and
oscillators
may
also be voltage controlled.
In
all
Instances, the
amount
of
change
In
the
sound
is
proportional to the
voltage applied to the control
circuit.
The same
sine-
wave
voltage
from
the
Sub
Oscillator that created
tremolo
in
the
VCA
when
applied to the control
in-
put
of
a
VCF
would
create
wah-wah,
or
when
applied
to
a
VCO
would
create vibrato.
It
is
not
at all
important
for
a
player to
understand
about
voltages
and
control
circuits
to
program and
play
the
GS-80.
When
you
set
the controls
and
levers
so the
sound
Is
"right,"
you
are
probably adjusting control
voltages.