User Manual

CHAPTER 23. LIVE INSTRUMENT REFERENCE 391
The phase of each oscillator can be adjusted using the Phase control in its display. With the
R (Retrigger) button enabled, the wavefor m restarts at the same position in its phase each
time a note is triggered. With R disabled, the oscillator is free-running.
As explained earlier oscillators can modulate each other when set up to do so with the
global display's algorithms. When an oscillator is modulating another oscillator, two main
properties dene the result: the amplitude of the modulating oscillator and the frequency
ratio between both oscillators. Any oscillator that is not modulated by another oscillator
can modulate itself, via the Feedback parameter in its display.
Aliasing
Aliasing distortion is a common side effect of all digital synthesis and is the result of the
nite sample rate and precision of digital systems. It mostly occurs at high frequencies. FM
synthesis is especially likely to produce this kind of effect, since one can easily create sounds
with lots of high harmonics. This also means that more complex oscillator waveforms, such
as Saw 32, tend to be more sensitive to aliasing than pure sine waves. Aliasing is a
two-fold beast: A bit of it can be exactly what is needed to create a cool sound, yet a bit
too much can make the timbre unplayable, as the perception of pitch is lost when high
notes suddenly fold back into arbitrary pitches. Operator minimizes aliasing by working in
a high-quality Antialias mode. This is on by default for new patches, but can be turned off
in the global section. The Tone parameter in the global section also allows for controlling
aliasing. Its effect is sometimes similar to a lowpass lter, but this depends on the nature of
the sound itself and cannot generally be predicted. If you want to familiarize yourself with
the sound of aliasing, turn Tone up fully and play a few very high notes. You will most likely
notice that some notes sound completely different from other notes. Now, turn Tone down
and the effect will be reduced, but the sound will be less bright.