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Chapter 3 ES2 38
Use pulse width modulation in ES2
You can alter the tonal color of rectangular waveforms by scaling the width of waveform pulses
to any value. This is known as pulse width modulation.
ES2 pulse width modulation features are extensive. For example, if rectangular waves are chosen
for all oscillators, you can simultaneously modulate the pulse width of oscillator 1 and the
synchronized pulse waves of oscillator 2 (or the square wave of oscillator 2’s ring modulator) and
oscillator 3.
Set a basic pulse width in oscillator 2 or 3
m Drag the waveform rotary control that surrounds the Wave knob (see the highlighted area in the
image above).
Only oscillators 2 and 3 allow you to dene a base (default) pulse width, prior to any pulse
width modulation.
Set up a pulse width modulation (of oscillator 1) in the router
1 Choose a rectangle wave for oscillator 1.
2 In the router, choose Osc1Wave as the target, and LFO1 as the source.
3 Adjust the modulation amount slider (try a value of 0.12).
4 Choose a sine wave for LFO 1.
5 Adjust the LFO 1 Rate (around 0.160 Hz for a slow sweep).
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 492 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.