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Table Of Contents
Cutoff Frequency
The cutoff frequency, or cutoff, as the name suggests, determines where the signal is cut
off. Simpler synthesizers offer only lowpass filters. Thus, if a signal contains frequencies
that range from 20 to 4000 Hz, and a cutoff frequency is set at 2500 Hz, frequencies above
2500 Hz are filtered. The lowpass filter allows frequencies below the cutoff point of 2500 Hz
to pass through, unaffected.
The figure below shows an overview of a sawtooth wave (A = 220 Hz). The filter is open,
with cutoff set to its maximum value. In other words, this waveform is not being filtered.
The figure below shows a sawtooth wave with the filter cutoff set to about a 50% value.
This filter setting results in suppression of the higher frequencies and a rounding of the
edges of the sawtooth wave, making it resemble a sine wave. Sonically, this setting makes
the sound much softer and less brassy.
As you can see from this example, use of the filters to cut away portions of the frequency
spectrum alters the waveform’s shape, thus changing the timbre of the sound.
359Appendix Synthesizer Basics