Filter
A further important feature of the filter is the RESONANCE control. Frequencies at the cut-off
point are increased in volume by this control:
Cutoff frequency
As you can see, those harmonics around the cutoff frequency are actually boosted in level
whilst all those outside the shaded area are removed. This is useful for emphasising certain
harmonics of the sound and with increased resonance settings, sweeping the cutoff
frequency up and down causes the filter sound to change from the normal ‘waa’ sound to a
more distinctive ‘weeow’ as the individual harmonics are picked out and emphasised.
As the RESONANCE is increased, a whistling like quality will be introduced to the sound
passing through the filter. When set to very high levels, RESONANCE actually causes the filter
to self - oscillate whenever a signal is being passed through it. The resulting whistling tone
being produced is actually a pure sine wave, the pitch of which depends on the setting of the
FREQUENCY knob (the filter’s cut-off point). This resonance-produced sine wave can actually
be used for some sounds as an additional sound source if desired.
15 Synthesis Tutorial
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