Section V: Synthesizers - Yamaha CS-50 Instruction Manual

SECTION
V - UNDERSTANDING SYNTHES*
iRS i
42
This section
fitsi
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
themselves to simple explanations. The
balance of
the
section provides
an overview of
how
the
CS-scries
synthesizers operate,
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
operates 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.
What
is
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 providing
an
infinite variety
of adjustable sounds.
The
CS-50 and
CS-60
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
14
on
the
CS-50 and
8
on
the CS-60).
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.
What Are
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
VCA,
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,
VCA's and
EG's:
8
sets
on
the
CS-60
for creating
each of the 8
notes
that can be played simultaneously,
and 4
sets
on
the CS-50
for
creating each of the 4 notes
that can
be
played simultaneously.
Why
Are Voltage Controlled
Circuits
Used
in
Synthesizers
&
How
Do 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 (AC),
such
as
the slow
sine
wave from the
synthesizer'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
Oscillator section.)
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
moving
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 manu-
ally controlled circuits.
Amplifiers (VCA'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 input
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 synthesizer.
When
you
set
the controls
and
levers so
the
sound
is
"right,"
you
are probably
adjusting control
voltages.