GAIA Exploring Sound (PDF) - Roland Corporation Australia

If we were to lower the bass control, and raise the treble:
Figure 4.4 Bass down, Treble up
remove any larger particles or impurities. This is another type of
filter.
Remember how we explained Subtractive Synthesis? We said
that we were “subtracting Harmonics.” So, unlike the tone
controls in Figure 4.3, we could better represent the shape of a
Filter control with this diagram:
Figure 4.5 Extreme Filter
Notice how we hear the changes. By raising the bass control we
can emphasize the sound of the bass, or we could lower its
sound by lowering the bass tone control. The same for the
piccolo using the treble control. However, even at extreme
settings we can still hear both instruments.
So now recall what happened in Lesson Three when we lowered
the “Tone Control” on the GAIA. The control labelled “Cutoff.” At
it’s extreme low setting we were able to completely remove all
sound. So it is very clear that the Tone Control of the GAIA is
much more powerful than that of a stereo amplifier.
The Filter
Perhaps you have studied Chemistry and used filters before. In
that case you will know that you can remove particles from a
liquid by passing the liquid through a paper filter. Or perhaps
while cooking you have passed flour through a sieve in order to
Level
Frequency
It shows the Harmonic series of a Sawtooth waveform as we
discovered in Lesson Three. Notice how the top two Harmonics
have not just been lowered, as with a typical tone control. They
have been removed altogether. To put it another way, they have
been “cut off.”
So we refer to the point shown by the arrow as “The Cutoff
Frequency,” or just Cutoff for short. All harmonics above the
Cutoff have been removed, and all those below the Cutoff are
allowed to pass through the filter.
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