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Generating audio with frequency modulation
The Sound Forge FM Synthesis feature can be used to create complex sounds from simple waveforms using frequency modulation (FM).
In frequency modulation, the frequency of a waveform (carrier) is modulated by the output of another waveform (modulator) to create
a new waveform. If the frequency of the modulator is low, the carrier is detuned slowly over time. If the frequency of the modulator is
high, the carrier is modulated so quickly that numerous additional frequencies (or sidebands) will be created.
Using the FM Synthesis tool, up to four waveforms (operators) can be used in a variety of configurations. Depending on the
configuration, a waveform can be a carrier, a modulator, or a simple, unmodulated waveform.
Generating a waveform
1.
From the Insert menu, choose Synthesis, and choose FM from the submenu. The FM Synthesis dialog appears.
Tip:
You can also click the FM Synthesis button ( ) on the Insert toolbar.
2.
Specify the length (in seconds) of the generated waveform in the Total output waveform length box.
3.
Use the Configuration slider to configure the arrangement and number of operators used to generate the waveform. For more
information, see Specifying the number and arrangement of operators on page 157.
4.
Modify individual operators as needed. For more information, see Modifying an operator on page 158.
5.
From the Insert waveform at drop-down list, choose a position to determine where the generated waveform is placed in the file.
6.
Click OK.
Specifying the number and arrangement of operators
Dragging the Configuration slider changes the graphical representation of the arrangement and number of operators used to generate
the waveform. When configuring your waveform, keep the following guidelines in mind:
• The outputs of horizontally joined operators are simply mixed. The outputs of the bottom operators are mixed to form the final
output. Mixing unique simple waveforms is referred to as additive synthesis.
• Operators joined vertically are FM carrier-modulator pairs. The bottom operator is the carrier and the top operator is the modulator.
• Operators without other operators directly above are simple waveform generators.
• When three or more operators are stacked, the top operator modulates the operator below it, which modulates the following
operator, and so on.
EDITING, REPAIRING, AND SYNTHESIZING AUDIO | 157