24
Advanced Features
The Oscillator Menu (FM Synthesis)
It can be seen that the resulting synced waveform has subsequently
been modified into a different shape. Altering a waveform’s shape in
this way introduces new harmonics into the sound which gives the
resulting waveform its distinctive synced sound qualities.
It should be realised that the greater the difference in tuning between
the Oscillator waveforms, the more pronounced the sync effect will
become, since more drastic changes will be made to the final synced
waveform. Changing the pitch of one of the Oscillators during the dura-
tion of a note (for example, modulated by an LFO) will add a dynamic
quality to the synced sound.
FM Synthesis.
The next two 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 intro-
duced. 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 com-
plex waveform.
The following diagram illustrates that the higher the modulation
between the Modulating wave and the Carrier wave, the more the
waveform changes.
In the 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 carrier 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 illus-
trated below.
It can be seen that the output waveform begins, being identical to the
carrier, but becomes more complex (harmonics are added) as the
amount of FM modulation increases via the envelope. It then returns to
a simple wave again as the envelope decays.
The timbre of the Waveform is changing with time. This is the opposite
of subtractive synthesis where a low pass Filter is used to remove har-
monics.
To complete a simple synthesizer, a further envelope is added to con-
trol the output volume.
The complete FM building block is illustrated below.
OSC 2 is able to FM OSC 3 via a dedicated FM envelope. It is impor-
tant that it is realized that this Envelope is used only for FM purposes
and is not one of the Envelopes available on the K-Station’s front
panel.
The diagram below shows in block diagram format how the K-Station
can produce FM sounds.
The easiest way to be totally familiar with FM is to take one of the fac-
tory preset FM sounds, for example Bank 2 - 09 (Sound 209), a bell
sound and to experiment by modifying the various FM settings.
OSC 2 - 3 FM Manual Level (Menu Page 9)
Controls the amount that Oscillator 3 is directly Frequency Modulated
by Oscillator 2. Whilst playing a note, adjust this value by using the
DATA knob. Notice that increasing amounts of modulation level make
the sound more metallic.
OSC 2 - 3 FM Envelope Amount (Menu Page 10)
Many sounds have complex harmonic movements at the start of the
sound. Introducing envelope modulation from an envelope with a fast
attack and decay time to control the FM amount will simulate this fast
changing harmonic effect.
Adjust this value by using the DATA knob. Notice how the ‘spit’ at the
beginning of the sound may be accentuated. Experiment with Oscillator
2’s pitch using the OCTAVE button and the SEMITONE and DETUNE
knobs.
Adjusting the FM Envelope Attack and Decay Times
Changing the various FM Envelope values is done from within the
Envelopes Menu. See Page 27 for details.
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