Next let’s look at the Filter Shell section. Filters are a crucial part of any synthesizer, so much so that filter types can be a deal breaker for some synth enthusiasts. What a filter does, is “filter” out a select range of frequencies from a sound.
There are many types of filters, but the ones most commonly found on synths are:
- Lowpass Filters – Allow you to cut off the sound above a desired frequency
- Highpass Filters – Allow you to cut off the sound below a desired frequency
- Bandpass Filters – Allow you to cut off the sound above and below a desired frequency
- Notch Filters – Allow you to cut off a desired frequency while leaving the higher and lower frequencies intact.
Below is Operator’s Filter Shell. It has all the types of filters listed above with variations on each of them, allowing for in-depth control over the sound.
- The Filter On/Off button does as expected: it turns the filter on and off.
- The Filter Type dropdown menu allows you to select the type of filter.
- Filter Frequency sets your desired cutoff frequency for the selected filter.
- And then there’s Filter Resonance. Resonance boosts the frequencies at the frequency cutoff point. Higher and lower resonance settings can really affect the tonal qualities of the filter.
In the video below, I use a Lowpass Filter to slowly sweep down and cut off the higher frequencies. I sweep the filter three times from open to closed and each time uses a higher resonance setting. Watch the video a few times and listen to the quality of the filter sweep. The last sweep with the highest resonance settings sounds squelchy and wet as it moves down the spectrum.
As you listen, you can watch what happens to the sound in the frequency spectrum.
Let’s start adding some depth to a patch.
Make sure your algorithm setting is set so that none of the oscillators modulate each other:
Set Oscillator A to:
- Wave: Sin
- Coarse: 1
- Level: 0.0 dB
Oscillator A envelope settings:
- Attack: 10.0 ms
- Decay: 100 ms
- Sustain: -10 dB
- Release: 2.00 s
Add Oscillator B with the settings:
- Wave: Saw64
- Coarse: 2
- Level: -10 dB
Oscillator B envelope settings:
- Attack: 20.00 ms
- Decay: 3.00 s
- Sustain: -2 dB
- Release: 1.5 s
And Oscillator C with the settings:
- Wave: Square64
- Coarse: 0.5
- Level: -18 dB
Oscillator C envelope settings:
- Attack: 20.0 ms
- Sustain: 0.0 dB
- Release: 500 ms
Turn on the filter in the Filter Shell section and select these filter settings:
- Type: Low Ladder
- Frequency: 1.3 kH
- Resonance: 2.00
With the Filter Shell selected, check out the Operator display. The filter has its own envelope independent of the oscillators.
Set the Filter Envelope to:
- Attack: 103 ms
- Decay: 2.29 s
- Sustain: 0.0 %
- Release: 2.00 s
- Envelope: 26 %
With these settings, you can hear the filter envelope opening and closing the filter, giving some movement and life to the patch.