Yamaha CS-15 Owner's Manual page 5

number
of
vibrations, such
as 2-fold, 3-fold,
and
so
on.
It is
seen
that the
waveform
will
gradually
come
to
resemble
a
sawtooth waveform.
In addition to
this,
it
is
apparent
that
this
sawtooth waveform
has
a
cycle similar to that
of
the
sine
wave
that has
been
used
as the
basis.
The
sine
wave
with
the basic cycle
is
referred to
as
the
fundamental and
the sine
waves of
harmonic overtones
as the
harmonics.
In the
case
of
musical instruments,
the
way
in
which harmonics
are
contained
in
sounds
will
depend on
the
arrangement
by which sounds
are
generated.
When we
discuss the
difference
in
tones (waveforms),
it is
the
same
as
dis-
cussing
what
kind of harmonics
the sounds
contain.
Accordingly, one
can express
the three
elements of
sound
in
another manner,
that
is,
as
1)
pitch. 2)
the
manner
in
which harmonics
are
contained (harmonic
structure) and
3)
volume.
SAWTOOTH WOVE
r
Leve
FwndouT'erftal"
^
Amplftude
;
^
2f
3f
3
4-f
4-
Harmcn;c$
STRUCTURE
OF
THE SYNTHESIZER
In the
synthesizer,
sounds
are synthesized by
electronically effecting control
on
the four properties
of
sound
(the three elements of sound
plus the
envelope), dividing
it
into
4
blocks.
Control of
pitch
is
effected
by
the
VCO,
that
of
harmonic spectrum by
the
VCF,
that
of volume by
the
VCA
and
that
of envelope by
the
EG
(envelope
generator).
The
following describes
the functions
of
each block.
CZhanae
of unxveform
o
Change
o\
harmonics.
r r
c>
OMf
F-
>
harmonics
^
-f
c
F
i
h&mwcs
In
addition
to adjusting the cut-off frequency by
means
of
a
knob,
the tone
is
caused
to
undergo
a
temporal change (from
the time
the
sound
is
generated
to the time
it
ceases) to give
it
an "enve-
lope".
This
is
accomplished by
effecting control
on
the
filter's
cut-off frequencies
by means
of
the
envelope
generator.
VCA
The
VCA
block adds an "envelope"
to the
volume.
The
process
starting
from
the
generation of
the
sound
up
to the point the sound
gradually fades
away
is
governed by
the
envelope
generator's
ATTACK
TIME,
DECAY
TIME,
SUSTAIN LEVEL, RELEASE
TIME
(A.D.S.R.),
changing
the amplification
degree of the
VCA
amplifier.
VCA
and Envelope
Storwd -fvam
VCF
fnuelope
VCP\
Output
VCO
The
VCO
block produces sound sources of
fre-
quencies corresponding
to the intervals
of
the key-
board.
The
sound
source
waveforms produced by
the
VCO
are
sawtooth waves and
square
waves
that
include
many
harmonics
in a
regular
manner. These
waves
are oscillated, using
an
electronic
circuit.
VCF
The
VCF
block determines
the tone, changing the
harmonic spectrum
of
the
sound
sources
by
cutting,
or emphasizing,
certain parts of the
harmonics by
passing the
sound
sources through
filters.
The
boundary between
the portion that passes
through
the
filter
and
the
portion
that
is
cut off
is
known
as
the cut-off frequency.
The
VCF
creates the charac-
teristic
harmonic spectrum, by
varying the cut-off
frequency.
The
signals
from
the
VCO
reach the
VCF
where
they
undergo
a
change with
regard
to their
harmonic
spectrum by
being passed through
a
filter.
The
sig-
nals,
now
containing
certain
tone
characteristics, are
given
a
volume "envelope"
at
the
VCA
and
then fed
out. In
this
way,
all
elements of
the properties of
sound
are
controlled
electronically,
by
utilizing the
three
elements of sound and
the "envelope."
The
synthesizer
has, in addition to the blocks described
above, other blocks such
as
the
LFO
which
permit
further changes
in
the sounds.
But
in
this case too,
the job
is
performed by
controlling the three
ele-
ments
of sound and
the envelope.
We
hope
that the points described
in this
section
may
be
helpful to
understand
the
immense
possibili-
ties
and
great pleasure awaiting
you on
a
path
that
will
lead
you
into
a
new
world
of music using
a
totally
new
musical instrument,
the synthesizer.
©