Yamaha TX 802 Owner's Manual page 27

WHAT'S
FM?
FIXED
FREQUENCY
An
operator can
also be set to Fixed mode, which
will
cause
it
to
produce
the
same
frequency
regardless of
what
key
is
pressed.
In
Fixed
mode,
the
frequency
is
displayed
in
Hz
(cycles
per second)
or
KHz
(1
000
cycles
per second).
If
carrier
is in
Ratio
mode
and
the
modulator
is in
Fixed
mode,
the
harmonic
structure of the
sound
will
change depending on
the key you
press.
LFO
The LFO (Low Frequency
Oscillator)
produces
a
slow
(i.e.
below
an
audible frequency) vibration that can be
used
to
create
vibrato,
tremolo
or other
effects.
If
the
LFO
is
affecting the output
level
of a
carrier,
the
result
will
be
Tremolo
(periodic
change
in
volume), and
if it is
affecting the output
level of
a
modulator, the
result will
be
periodic
change
in
tone
("Wan-Wan"). The LFO
can
also control the pitch of the operators, producing
Vibrato
(periodic
change
in
pitch).
SENSITIVITY
Acoustic instruments produce
different
sounds
when
played
softly
or
loudly.
Not
only the loudness, but also
the tone changes.
A
softly
played note
is
usually softer
in
tone as
well
as volume.
FM
synthesis provides an
easy
way
to
simulate
this.
Each operator can be "Velocity
Sensitive", and
adjust
its
output
level
according
to
how
hard
a
key
is
struck
(key velocity).
If
a carrier
is
velocity sensitive,
the
volume
will
depend on
the key
velocity.
If
a
modulator
is
velocity sensitive,
the tone
will
depend
on the key
velocity.
^
DETUNE
The harmonic
structure of actual acoustic
sounds
is
usually
somewhat
"irregular".
This
makes them
sound
interesting
and
lifelike.
By
slightly
Detuning each
operator,
you can
create
this
type of naturally
irregular
sound.
SCALING
The
tonal characteristics of an instrument
generally
change from
note
to note.
For example, high notes on
a
piano
have
a
simpler
harmonic
structure
than the bass
notes.
By
Scaling the output
level
of
a
modulator
to
decrease
as
you
play
up the keyboard, you can
simulate
this.
LEARNING
FM
SYNTHESIS
Creating
a
voice
from
the
initial
setting
is
not
a
simple
matter.
The
best
way
to learn
about
FM
synthesis
is
to
get
inside
the factory preset voices and see
how
they work. Turn each
operator
off
one
by
one,
and see
how
each operator
affects
the sound.
Make
small
changes
in
operator output
level
or
EG
rates.
Try
starting
from
a
preset voice that
is
fairly
close to
what
you have
in
mind,
and
edit
it
to
your
liking.
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