Apple Logic Express 7 - Manual (Page 126)

126 Chapter 19 EXSP24
Highpass (HP)
The Highpass Filter is a 2 pole (12 dB/Oct.) design. A Highpass filter reduces the level of
frequencies that fall below the cutoff frequency. It is useful for situations where you
would like to suppress the bass and bass drum in a sample, for example, or for creating
classic highpass filter sweeps.
Bandpass (BP)
The Bandpass Filter is a 2 pole (12 dB/Oct.) design. A Bandpass filter only allows the
frequency bands directly surrounding the cutoff frequency to pass. Frequencies which
fall outside these boundaries will be cut.
Drive
This knob allows the filter input to be overdriven. Turning Drive up leads to a more
dense and saturated signal, with additional harmonics being introduced/becoming
audible.
Cutoff
The cutoff frequency of the lowpass filter. As you turn this knob to the left, an
increasing number of high frequencies are filtered from the signal. The Cutoff value also
serves as the starting point for any modulation involving the filter.
Resonance
Turning up Resonance leads to an emphasis of the frequency area surrounding the
frequency defined by the Cutoff parameter. Very high Resonance values introduce self
oscillation, and cause the filter to produce a sound (a sine wave) on its own.
Simultaneous Control of Cutoff and Resonance
By clicking and dragging on the chain symbol located between the Cutoff and the
Resonance knobs, you can control both parameters simultaneously: vertical mouse
movements alter Cutoff, and horizontal mouse movements affect Resonance values.
Key
This knob defines the amount of filter cutoff frequency as determined by note number.
When Key is fully turned to the left, the cutoff frequency is not affected by the note
number, and is identical for all notes played. When Key is set fully right, the cutoff
frequency follows the note number 1:1—if you play one octave higher, Cutoff is also
shifted by one octave. This parameter is very useful in avoiding overly filtered high
notes.