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Chapter 3 ES2 40
Use frequency modulation in ES2
The principle of frequency modulation (FM) synthesis was developed in the late 1960s and early
1970s by John Chowning. It was popularized by Yamaha’s range of DX synthesizers in the 1980s.
Although the ES2 can’t be compared with the DX series in the discipline of pure FM synthesis, it
can achieve some of the signature sounds of these instruments.
In pure FM synthesis, the frequency of one signal generator, or oscillator, is altered (modulated)
by another signal generator. Positive values from the second generator increase the frequency
of the rst generator. Negative values decrease the frequency. In a synthesizer, this type of
modulation takes place in the audible range. Depending on the design of the instrument, you
can hear the signals of either the rst oscillator alone (being modulated by the other oscillator),
or both oscillators. The interaction between the two generators alters the waveform signal of the
rst oscillator and introduces a number of new harmonics. This harmonic spectrum can then be
used as the source signal for further sound processing, such as ltering, envelope control, and so
on. See Frequency modulation (FM) synthesis on page 493 for further information.
In ES2, the frequency of oscillator 1 (with a sine wave chosen—11 o’clock position for the Wave
knob) can be modulated by the output signal of oscillator 2.
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When oscillator 2 outputs a positive signal, the frequency of oscillator 1 increases.
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When oscillator 2 outputs a negative signal, the frequency of oscillator 1 decreases.
The net eect of speeding up or slowing down the frequency of oscillator 1 in each waveform
cycle is a distortion of the basic wave shape. This waveform distortion also has the side benet of
introducing a number of new, audible harmonics.
Important: The impact of any frequency modulations you perform depends on both the
frequency ratio and the modulation intensity of the two oscillators.
The “pure” FM synthesis method uses a sine wave for both the rst and second signal generator
(both oscillator 1 and 2 would be limited to generating a sine wave in ES2 if you stuck with this
approach). ES2, however, provides 100 Digiwaves and countless combinations of modulation
intensities and frequency ratios that can be used for either oscillator. This provides a vast pool of
harmonic spectra and tonal colors for you to experiment with.
Tip: The type of modulation that occurs can vary signicantly when dierent waveforms are
chosen for oscillator 2—the modulating oscillator—in particular.
Set the frequency ratio and adjust the modulation intensity
1 Adjust the Frequency (coarse and ne tune) parameter values of one, or both, oscillators.
2 Click (or drag) in the control range between the Sine and FM icons around the oscillator 1 Wave
knob.
This determines the amount, or intensity, of frequency modulation.