WHAT
IS
A SYNTHESIZER
Unlike other musical instruments, the synthesizer has
no
fixed
sound of its
own. Thus, before playing it, it is
necessary to shape the sounds. But
with
the
synthesizer
you will be able to create, with your own liands and by
synthesizing
sounds, a
new type of sound that can never
be made by any other musical instrument.
•
THE THREE ELEMENTS
OF
SOUND
How
does a synthesizer
make
sounds?
Before
explaining the principle of the synthesizer, let us
consider what kind of properties sound has.
Sound produced by musical instruments such as
the piano or the guitar has a certain pitch,
according
to the
key
or string used.
It
is possible to change
the
pitch by changing the length of
the vibrating portion
of the string.
In
this case, the string's
nuinber of
vibrations per second also
changes. The slower the
string vibrates, the
lower the pitcii becomes. In this
way, it is possible to express the difference in pitch
by the number
of vibrations (frequency).
PITCHES
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However, between
the
sound of
a
piano
and
that
of a guitar there is a
difference in tone even when
both sounds are of the same
pitch:
no one
will mis-
take the sound of
the
piano for that
of the
guitar.
This
is because there is a difference in the way the
strings vibrate (tlie vibration
waveform
),
due to
the
difference
in the
arrangement by which
the
sounds
are generated, and because of the difference in the
shape and size of the musical instruments.
TONES
jDifferetlca
(n
-tones
means
PIOMO
Furthermore, even when both the pitch and
tone
quality are the same there can be a
difference in
sound,
such as
when the
same
key of the piano is hit
in
a
forcible or
a
gentle manner.
It
is easy to discern
the two sounds trom each other because of the
magnitude
(volume) of the sound.
This is
because
a
difference will be
produced in
the
size and amplitude
of the string's
vibrations,
due to the intensity
with
which
it has been struck.
In
this way,
sounds produced
by musical instru-
ments
have such elements
as
pitch,
tone and
volume,
whose
differences
add to the sound's
characteristics.
These
elements
are referred to
as
"the
three elements
of sound",
which may also
be considered as the
difference in frequency,
waveform
and amplitude.
•
TEMPORAL CHANGE
IN
SOUNDS
However,
the elements
which
render
sounds with
certain
ciiaractcristics
are not confined
to these
three. Taking
the piano for
example, the
volume will
reach
maximum the
instant the
key
is hit, then
will
decrease
graduahy. When
the finger
is released from
the keyboard,
the sound
will fade out.
In the
case
of
the organ, the
action of depressing
the
key
will
cause
the
volume to rise to
a certain
level, which will be
retanicd
for
the duration
the keyboard
is depressed.
The
sound
will fade away
when the finger is
released
from
the key.
Ktr
ON
In
such musical
instruments
as
the trumpet, for
example, the harmonic spectrum changes
together
with
the change
in volume. The
tone
changes too,
along with the passage of time.
Thus, the sounds of musical instruments
undergo
delicate changes from the time the sound is
generated
to the time it fades away. These temporal
changes are
known
as an
"envelope."
HARMOMICS
What must we
do in
order
to produce electrical
sounds that
have
the above mentioned three elements
of sound, these are pitch, tone and volume,
and which
vary with time (have an envelope)?
Before
going into
the matter, let us view sound again from a
different
angle
.
As regards the vibration waveforms by which the
tone is determined, it is
known
that any given
wave-
form
can be considered as
consisting
of a
certain
number of sine waves. !n other words, all
waveforms
can be produced by combining a large
number of
sine waves.
For
example, let us overlap over a single
sine
wave waveforms
having an
integral multiple
o
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