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Appendix B Synthesizer Basics 484
Resonance
The resonance control emphasizes or suppresses signals around the cuto frequency.
The gure below shows an ES1 sawtooth wave with a high resonance setting and the cuto
frequency set to 660 Hz.
This resonant lter setting results in much brighter and harsher signals close to the cuto
frequency. Frequencies below the cuto point are not aected.
The result of using lter resonance is a change in the basic waveform shape and, therefore, the
timbre of the sound.
Very high lter resonance settings can cause the lter to self-oscillate, resulting in the lter
generating an audible sine wave.
Filter drive
Filter drive adds an amount of gain to the waveform as it enters the lter—an input gain
control—overdriving the lter and distorting the waveform. This waveform distortion changes
the timbre of the sound, making it much harsher.
The gure shows an unltered sawtooth wave, with drive set to a value of 80%. Note the wave
cycles touching the oor and ceiling of the lter’s dynamic range.