Shapers
Filter
Voltage-controlled filter — removes some frequencies to change the tone. The most expressive module in a synth.
Learn about it in Filters: carving the sound
How it works
LP (low-pass) lets lows through and cuts highs — turning Cutoff down makes it darker. HP does the opposite, BP keeps only a band, NOTCH removes one. Res(onance) boosts the frequencies right at the cutoff for a squelchy, whistling peak. The cutoff can be moved by signals: CV is scaled by CV Amt (±1.0 × 100% = ±4 octaves), V/OCT moves exactly 1 octave per 1.0.
Inputs
| IN | The audio to filter. |
|---|---|
| CV | Moves the cutoff, scaled by CV Amt. Patch an LFO here for a sweep, or an ADSR for a “wow” on every note. |
| V/OCT | Key tracking — moves the cutoff 1 octave per 1.0, so patch the same pitch signal your VCO gets and high notes stay as bright as low ones. |
Outputs
| OUT | Filtered audio. |
|---|
Knobs and switches
| LP / BP / HP / NOTCH | Filter type. |
|---|---|
| Cutoff | The centre point that CV moves around. |
| Res | Resonance — emphasis at the cutoff. |
| CV Amt | How far the CV input moves the cutoff. Negative = inverted (CV closes the filter). |
Patches to try
- Filter sweep with an LFO: VCO SAW → Filter IN, LFO ± → Filter CV, Filter OUT → Output. Set Cutoff around 800 Hz, Res ~10, then raise CV Amt. LFO Rate sets the sweep speed; LFO Depth × CV Amt sets how wide it is.
- Use the LFO “+” output instead of “±” to only sweep upward from the Cutoff knob.
Lessons that use the Filter
Each one opens as a working patch in the synth.
- 03 · Subtractive Synthesis
- 04 · Movement with LFOs
- 05 · Mixer: Fat Sounds
- 07 · Clock & Sequencer
- 11 · Noise: Wind & Hats
- 17 · Wavetable & PWM
- 23 · Slew: Glide Anything
- 24 · Scale/Offset: Signal Surgery
- 25 · Chords & Arpeggios
- 26 · Polyphony: Play Chords
- 27 · Stereo & Sidechain
- 29 · Switch: A New Melody Every Bar
- 37 · XY Pad: Play by Touch
- 38 · Lorenz: Chaos
- 41 · Gamepad & Phone Tilt
- 42 · Mic & Envelope Follower
Words to know
- Filter — Removes part of the frequency range, making a sound darker, thinner or more focused.
- Cutoff — The frequency where a filter starts cutting.
- Resonance — Boosts the frequencies right at a filter’s cutoff, adding a whistling, vocal peak.