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FM Tone Generation
Appendix
There are four main elements that determine the character of a voice:
(1) Each operator's output level.
(2) Each operator's frequency.
(3) The feedback level.
(4) Each operator's envelope generator (EG).

(1) Operator Output Level

The output levels of the operators are the most important parameters in editing a voice. Among these, the
output level of the modulator(s) has the greatest effect on the timbre or tonal quality of the voice. If a mod-
ulator's output level is set to “0” so that it does not modulate the carrier, the resulting output of the carrier
will be a simple sine wave (below). Increasing the output of the modulator increases the degree of modula-
tion and, hence, the amount of harmonics in the sound. Generally, the greater the modulator's output, the
brighter the sound will be. Extremely high values result in a harsh, noisy sound.
Since the carrier actually produces the sound, increasing the output level of a carrier increases the volume of
the sound. If there are two or more carriers, changing the output level of individual carriers may also affect
the timbre of the sound, since the volume balance of the different carriers is changed.

(2) Operator Output Frequency

The type of harmonics added to the carrier output by means of the modulator is determined by the ratio
between the frequencies of the modulator and carrier. For example, when two operators are combined verti-
cally, and “F COARSE” for both of them is set to 1.00, the frequency ratio will be 1:1 and the first, second,
third and following whole number series harmonics will be generated in order. This type of harmonic config-
uration is called a sawtooth wave, and is used for making voices like brass, strings, or piano.
If the “F COARSE” for the modulation in this situation is changed to 2.00, the frequency ratio becomes 1:2,
and the odd numbered harmonics, the first, third and fifth and following harmonics will be generated. This
harmonic configuration is called a rectangular wave, and is used for creating woodwind voices for like clari-
net and oboe.
Furthermore, if “F FINE” is set so that the frequency ratio is not a whole number, many non-integer over-
tones will be produced. The sound can be used for creating metallic sounds, the noise when strings are hit
with something, or breath noise.
Voice Editing Essentials
A
B
A
B
A
B
The output level is
greatly increased.
The output level is
increased slightly.
Output Level = 0
Sine wave The waveform changes
slightly. The waveform changes a lot.
Modulator
Carrier