Waldorf Blofeld Keyboard - Manual (Page 101)

Sound Synthesis Basics
101 Blofeld User´s Manual
The Comb filter used to simulate a string or a
tube
The Comb filter is one of the most basic building blocks of
“Physical Modeling”, which is the term for an algorithmic
description of an acoustic instrument. The Blofeld is
definitely not meant to replace a good physical modeling
synthesizer, so you shouldn’t expect to get a perfect
emulation of an acoustic instrument like a trumpet or a
violin out of the Blofeld. However, the Comb filter
enables you to create abstractions of those sounds that
can be played expressively.
To do so, you have to understand that the Comb filter is
the part that actually sets the pitch of the resulting sound;
the oscillators or the noise generator are only used to
trigger the Comb filter somehow. When you play with the
Comb filter, you can hear that it emphasizes or attenuates
certain frequencies depending on the setting of Cutoff and
Resonance.
When you set Resonance to a very high value, you will
notice that the Comb filter oscillates heavily, and that’s
the key to using it as a tone generator. When you set
Filter Keytrack
to +100%, you can play the Comb filter
musically.
Now you need to know how to set up Cutoff. Filter Cutoff
is scaled in semitone steps, and you only have to find the
Cutoff value where the filter oscillates with standard pitch.
The following table gives you these settings:
Oscillator Comb+ Comb-
64’ 11 23
32’ 23 35
16’ 35 47
8’ 47 59
4’ 59 71
2’ 71 83
Comb Filter Cutoff settings
If you need other tunings, just keep in mind that Cutoff is
changed in semitones, so if you increment Cutoff by 12,
the filter oscillates one octave higher, and so forth.
☞
To set up the Comb filter to produce a tone:
1. Select either Comb+ to produce a string-like
tone or Comb- to produce a tube-like tone.
2. Turn up Resonance to around 114 to 127.