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178 Chapter 15 EFM1
FM Parameters
These parameters affect the frequency modulation aspects of the EFM 1.
FM (Intensity)
The modulator oscillator modulates the volume envelope frequency, resulting in newly
generated sidebands that add new overtones. Turning up the FM (Intensity) control
(the large dial in the center) produces increasing numbers of overtones—and the
sound becomes brighter. The FM (Intensity) parameter is sometimes called the FM
Index.
Note: Although the technology behind it is very different, you could compare the FM
(Intensity) parameter to the Filter Cutoff parameter of an analog synthesizer.
Modulation Env(elope)
To control the FM (Intensity) parameter dynamically, the EFM1 provides a dedicated
ADSR (FM) modulation envelope, consisting of four sliders: A (Attack time), D (Decay
time), S (Sustain level) and R (Release time). The envelope is triggered every time a MIDI
note is received. The Attack slider sets the time needed to reach the maximum
envelope level. The Decay slider sets the time needed to reach the Sustain level
(determined by the Sustain slider). The Sustain level is held until the MIDI note is
released. The Release slider sets the time needed to reach a level of zero, after the MIDI
note has been released.
FM Depth
The strength, or impact, of the modulation envelope on the FM intensity is determined
by the FM Depth control.
Turning the FM Depth control clockwise increases the effect of the modulation
envelope. Turning the FM Depth control counter clockwise inverts the effect of the
modulation envelope, meaning that the envelope slopes down during the Attack
phase, and slopes up during the Decay and Release time phases.
In the center (0) position, the envelope does not have an effect. You can easily center
the FM Depth dial by clicking on the 0.
Modulator Pitch
The impact of the modulation envelope on the pitch of the modulator oscillator is
determined by the Modulator Pitch control.
Turning the Modulator Pitch control clockwise increases the effect of the modulation
envelope. Turning the Modulator Pitch control counter-clockwise inverts the effect of
the modulation envelope, meaning that the envelope slopes down during the Attack
phase, and slopes up during the Decay and Release time phases.
In the center (0) position, the envelope does not have an effect. You can easily center
the Modulator Pitch dial by clicking on the 0 button.