ES1 filter parameters in Logic Pro for iPad
This section outlines the ES1 filter parameters.
Filter parameters
Cutoff knob and field: Set the cutoff frequency of the lowpass filter.- Resonance knob and field: Cut or boost the portions of the signal that surround the frequency defined by the Cutoff parameter. Boost can be set so intensively that the filter begins to oscillate by itself.
Filter Mode buttons: The lowpass filter offers four different slopes of band rejection above the cutoff frequency. Tap one of the buttons to choose a slope (amount of rejection, expressed in decibels (dB) per octave):
12 dB: Provides a soft, smooth sound that is reminiscent of the early Oberheim SEM synthesizer.
18 dB: Resembles the filter sound of the Roland TB-303.
24 Fat: Compensates for the reduction of low frequency content caused by high Resonance values. This resembles the behavior of an Oberheim filter.
24 dB: Mimics the behavior of a Moog filter. Increase the Resonance parameter value to reduce the low end of the signal.
Drive knob and field: Change the behavior of the Resonance parameter, which eventually distorts the sound of the waveform. Drive is actually an input level control, which allows you to overdrive the filter.
Filter Boost button: Increase the output of the filter by approximately 10 decibels. The filter input has a corresponding decrease of approximately 10 decibels, maintaining the overall level. This parameter is particularly useful when applying high Resonance values.
Key Follow slider and field: Set the effect that keyboard pitch (the note number) has on filter cutoff frequency modulation.
If Key Follow is set to zero, the cutoff frequency does not change, no matter which key you strike. This makes the lower notes sound comparatively brighter than higher notes.
If Key Follow is set to maximum, the filter follows the pitch, resulting in a constant relationship between cutoff frequency and pitch. This mirrors the properties of many acoustic instruments, where higher notes sound both brighter in tone and higher in pitch.
ADSR Vel Min/Max sliders and fields: Determine how note velocity affects modulation of the filter cutoff frequency with the envelope generator. Use the sliders to set minimum and maximum velocity range values. The greater the distance between the sliders, the more filter cutoff is affected by incoming velocity messages. See ES1 envelope parameters.
Output a sine wave from the filter
If you increase the filter Resonance parameter to higher values, the filter begins to internally feed back and, as a consequence, begins to self-oscillate. This results in a sine oscillation—a sine wave—that is actually audible.
You can make the ES1 filter output a sine wave by following the steps below. This lets you play the filter-generated sine wave with the keyboard.
In Logic Pro, switch the Sub Osc Wave knob to Off.
Drag the Osc Mix slider to the very bottom (Sub).
Set the Resonance knob to the maximum position.
If you wish, tap the Filter Boost button.
Filter Boost increases the output of the filter by approximately 10 decibels, making the self-oscillation signal much louder.
Play notes on your MIDI keyboard or the onscreen keyboard.
Control filter cutoff with velocity
The envelope generator modulates the filter cutoff frequency over the course of a note duration. The modulation intensity and response to velocity information is set with the ADSR Vel Min/Max sliders. The envelope generator also controls the level of the sound over time.
In the Logic Pro ES1 Filter section, set the minimum and maximum amount of modulation with the ADSR Vel Min/Max sliders and fields.
The difference between the ADSR Vel Min/Max sliders indicates the dynamic range of this modulation.
Set the ADSR sliders to the values you want to use, and adjust the ADSR Vel Min/Max sliders as needed.
Tip: If you’re unfamiliar with these parameters, set the Cutoff parameter to a low value, Resonance to a high value, and move both ADSR Vel Min/Max sliders upward. Constantly strike a note on the keyboard while changing the sliders to learn how these parameters work.
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