Oscillator Start Phase
When synthesizing percussive or plucked type sounds, where
there is a lot of detailed waveform information at the beginning
of the sound, it is often useful to have the Oscillator wave start
in exactly the same place every time a key is pressed.
The start phase option allows the precise starting point of the
Oscillator wave to be determined. At zero, the wave will start at
zero Degrees. Each increment on the display shifts the start
point of the wave approximately 24 degrees. The wave will start
at a random phase when set to o F (off).
FM Synthesis.
The next four menu options allow sounds based on FM
(Frequency Modulation) synthesis to be created. Before looking
at the operations of these controls, a little explanation of FM
synthesis follows.
Earlier in this manual, the basics of subtractive synthesis were
introduced. Terms such as harmonics, timbre, waveforms and
oscillators became familiar.
FM Synthesis is the technique of using one waveform to
Frequency Modulate - FM- another to produce a resultant more
harmonically complex waveform.
The following diagram illustrates that the higher the modulation
between the Modulating wave and the Carrier wave, the more
the waveform changes. In this illustration the Oscillators are
producing Sine waves. It is the change in harmonics over time
that makes a sound interesting to our ears. In FM synthesis, an
envelope generator is inserted between the modulator and car-
rier waveforms so that there is control over of how much of the
frequency modulation is taking place with respect to time.
Adding this envelope constructs the basic FM building block as
illustrated below.
41
Oscillators - FM Synthesis
Advanced features
Modulator Oscillator
Modulator
Envelope modulation = 20
Modulation level = 0
= 30
= 90
Carrier Oscillator
Carrier
Output waveform
Output waveform
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