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Chapter 16 Synthesizer Basics 197
Cutoff and Resonance—illustrated with a sawtooth wave
This picture shows an overview of a sawtooth wave (a = 220 Hz); The filter is open, with
cutoff set to its maximum, and with no resonance applied. The screenshot shows the
output signal of Logic’s ES1, routed to a monophonic Logic Output Object. The
recording was performed with the Bounce function of this Audio Object, and is
displayed in Logic’s Sample Editor at a high zoom setting.
When Michelangelo was asked how he would manage to cut a lion out of a block of
stone, he answered, “I just cut away everything that doesn’t look like a lion”. This, in
essence, is how subtractive synthesis works: Just filter (cut away) those components of
sound which should not sound—in other words, you subtract parts of the oscillator
signal’s spectrum. After being filtered, a brilliant sounding sawtooth wave becomes a
smooth, warm sound without sharp treble. Analog and virtual analog synthesizers are
not the only devices that make use of subtractive synthesis techniques. Samplers and
sample players also do so, but use modules which play back digital recordings
(Samples) in place of oscillators (that supply sawtooth and other waveforms).
The picture below shows a sawtooth wave with the filter half closed (24 dB/Fat). The
effect of the filter is somewhat like a graphic equalizer, with a fader set to a given cutoff
frequency (the highest frequency being fed through) pulled all the way down (full
rejection), so that the highs are damped. With this setting, the edges of the sawtooth
wave are rounded, making it resemble a sine wave.
The wave length here is not really higher, but the zoom setting is.