Yamaha DX200 Specifications download pdf (Page 117)

117

FM Tone Generation

Appendix

Although the six operators can be combined in a wide variety of ways for many different sounds, here we'll

look at the fundamental combinations of just two operators, to help you understand the basics of FM synthe-

sis.

Two sine wave operators (labelled “A” and “B” here) can be combined in one of two ways: horizontally or

vertically.

(1) Horizontal Combination

When the two operators are combined horizontally, the sounds of the two are simply mixed together. This

combining of two or more different sounds is called additive synthesis.

(2) Vertical Combination

When the two operators are combined vertically, the sound of the top operator (B) “modulates” that of the

lower operator (A). In this situation, operator B produces no sound, but alters the sound of operator A, pro-

ducing a sound of greater harmonic complexity. This “stacking” of operators is called Frequency Modulation

(FM) synthesis.

To sum it up, when two operators are combined horizontally, both operators generate the sound; when com-

bined vertically, one operator changes the sound, the other produces it.

Combinations of Two Operators

A B

Mixed sound of A and B

Operator B changes or modulates the sound

of A (but produces no sound itself).

Operator A produces the actual sound, as

modulated by B.

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Yamaha DX200 Specifications Page 117