7

Chapter 22 ES2 237
Screenshot of an ES2 sample, created with the Bounce function of Logic. The pulse
width is modulated. It is easy to see how the width of the pulses varies between a
rectangular shape and very thin pulses. An LFO is selected as the modulation source,
and its waveform is a sine wave. You can see about half a phase of the sine wave. If a
rectangular wave had been selected for the LFO, you would see the pulse width
periodically changing between the two fixed extreme values.
Note: A pulse wave (with its width modulation controlled by an LFO set to a sine wave)
makes a single oscillator sound vivid, undulating, and rich with overtones. Sonically,
this is somewhat like the sound of two slightly detuned, phasing oscillators. The effect
sounds great with sustained bass and pad sounds. Select the intensity and speed of the
modulation with care, as the overall volume (and level of the first partial) decreases,
and slight detuning occurs, when the pulses become very thin (below 10%).
Note: Pulse width modulations via velocity sensitive envelope generators sound very
dynamic—a great effect, especially for percussive bass sounds.
Sync
You can see that the rectangular and sawtooth waveforms also feature a Sync option. In
this mode, the frequency of Oscillator 2 (or 3, respectively) is synchronized to the
frequency of Oscillator 1. This does not mean that their frequency controls are simply
disabled. They still oscillate at their selected frequencies, but every time that Oscillator
1 starts a new oscillation phase, the synchronized Oscillator is also forced to restart its
phase from the beginning. This is practical while the frequency of the synchronized
Oscillator is significantly higher than that of Oscillator 1.
The graphic shows the output signal of Oscillator 2, set to a synchronized sawtooth
wave. Its frequency is about three and a half times that of Oscillator 1. Oscillator 1 was
set to 0 semitones, and Oscillator 2 to +22 semitones. The oscillogram clearly shows
how the phase of Oscillator 2 is forced to restart after about three and a half phases.
Between the pulses of Oscillator 1, Oscillator 2 runs freely.