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FM Modulator Frequency

Macro: FMmodFreq

This sets the modulator frequency when Source is set to Sine. The main Frequency Entry Mode affects this control as well.

FM was a popular technique for synthesizing musical instrument tones, prior to the dominance of wavetable methods. It was particularly "noteworthy" for being the first reasonable method for creating decent brass-like sounds, and was used in many professional keyboard synthesizers. In recent years the technique has been unfairly maligned by association with the simplified one-chip synthesizer used in early inexpensive sound cards. Among musicians using professional equipment to create new sounds (as opposed to simply using the preset sounds or "patches" that came built into the intrument), there was the additional criticism that the technique was hard to control and non-intuitive. Nevertheless, there is still room for exploration.

FM synthesis typically uses modulation frequencies that are at particular ratios relative to the main wave frequency. If you want to experiment with this, try starting with the main wave at 440 Hz and the modulator at some particular ratio like 2:1 (880 Hz), or 3:2 (660 Hz), or 1:2 (220 Hz). Adjust the FM deviation to be around +/-400 Hz as well.

Now as you change the main frequency, you will also get a different ratio, and you will notice that not only does the pitch change but the timbre or tone color changes as well... sometimes quite dramatically. Make a note of the ratio when you find an interesting sound, and use it as a basis for further explorations with different deviations.

In FM synthesizers, the modulator is often a wave other than a simple sine, so you may also want to try Stream Modulation to explore more exotic modulators.

The resolution of this and all Generator frequency displays may be set between 0 and 9 decimal places via the Frequency Places option in the Frequency Step Mode dialog, invoked by clicking the button below the Main Freq control higher up in this FM dialog. (The button shows the current Step Mode, which defaults to Step Direct.)

Macro Notes:

L.1.FMmodFreq=100 sets the Left Stream 1 FM Modulation Frequency to 100 Hz.

FMmodFreq=>1 will increment or FMmodFreq=>-1 will decrement the current FM Modulator Frequency by 1 Frequency Step. Only +/-1 step is allowed per command, but the step size and type can be controlled via the Frequency Step dialog. Note: The Frequency Step setting affects the behavior of almost all Generator frequency controls.

See also Frequency Modulation, Frequency Modulation Dialog, Waveform Stream Controls


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