16-14
DSP Functions
The DSP Functions
One-pole Highpass Filter (HIPASS)
High-frequency partials pass through this filter unaffected. At the cutoff frequency, the signal is
attenuated 3 dB. There’s a roll-off of 6 dB per octave below the cutoff frequency. The resonance is
fixed at -3dB. When the cutoff frequency is well above the highest-frequency partials of a sound,
raising the cutoff further will not affect the timbre of the sound, but will merely attenuate it
further.
The Coarse Adjust parameter sets the cutoff frequency in terms of a key name. The remaining
parameters (except Pad) alter the cutoff frequency in increments of cents. Positive key tracking
values raise the cutoff frequency for high notes and lower it for low notes. More specifically, a
value of 100 cents per key on this page, when filtering a constant waveform like a sawtooth,
would result in waveforms of exactly the same shape for all pitches of the waveform. The cutoff
frequency moves in sync with the frequencies of the waveform’s partials as different pitches are
generated. Negative key tracking values will steepen the rolloff of highpass filters below the
cutoff. The Pad parameter, as always, attenuates the signal at the input to the function. These
parameters affect all the highpass filters similarly.
-50
-45
-40
-35
-30
-25
-20
-15
-10
-5
0
10 100 1000 10000 100000
Frequency in Hertz
Amplitude in dB
Cutoff frequency
from C 2 to C 7
C 2 C 7
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