Filters
A filter changes a sound by reducing selected frequency ranges. The cutoff sets where the reduction begins, so you can remove low-end rumble, soften high-frequency content, or shape the movement of a synth patch.
What a Filter Does
A filter lets some frequencies pass through while reducing others. The point where it starts working is called the cutoff frequency. The filter type determines which side of that point is kept.
The Main Filter Types
Low-Pass Filter (LPF)
Lets low frequencies pass while reducing highs. Moving the cutoff down removes more upper harmonics; moving it up leaves more of the original brightness in the sound.
Used for: Warm pads, muffled effects, filter sweeps, taming harsh synths
High-Pass Filter (HPF)
Lets high frequencies pass, blocks lows. Removes rumble, mud, and low-end weight. Makes sounds thinner and lighter. Essential in mixing to clean up tracks that don't need bass content.
Used for: Cleaning up vocals, thinning pads, lo-fi telephone effects, clearing low-end mud
Band-Pass Filter (BPF)
Only lets a band of frequencies through, blocking both highs and lows. Creates a narrow, focused, "radio-like" sound. Moving the band up and down the frequency range creates classic wah-wah and vocal-like effects.
Used for: Wah effects, vocal formants, isolating specific tones, creative sound design
Notch Filter (Band-Reject)
The opposite of band-pass - it cuts out a narrow band while letting everything else through. Used to surgically remove problem frequencies like feedback, hum, or resonances.
Used for: Removing feedback, cutting hum, phaser effects, surgical frequency removal
Resonance
Resonance (also called Q or emphasis) boosts the frequencies right at the cutoff point, creating a peak. Low resonance gives a gentle roll-off. High resonance creates a sharp, whistling, almost singing quality at the cutoff frequency.
Higher resonance creates a sharper peak at the cutoff, adding an "acid" or "squelchy" character.
The Classic Filter Sweep
A filter sweep automates a filter's cutoff over time. Opening a low-pass filter reveals more upper harmonics; closing it removes them. The timing of the movement, resonance, and other arrangement changes determine whether the sweep acts as a build, transition, or release.
Sweep Up (Opening)
Cutoff moves from low to high, revealing more upper harmonics. Automating the movement before a new section can create a gradual change in density.
Sweep Down (Closing)
Cutoff moves from high to low, reducing upper harmonics. This can thin a part for a transition or outro.
Production Tip
In almost every mix, put a high-pass filter on everything except your bass and kick drum. Set it around 80-120 Hz. This removes low-end rumble and mud that builds up when many instruments stack their inaudible low frequencies together. It's one of the simplest things you can do to clean up a mix.
Try it
Tap the same bright chord through different filter settings. This time the chord stays the same and the filter changes the tone.
Same chord, different filter settings.
Key takeaway
Filters remove frequencies to shape tone. Low-pass cuts brightness, high-pass cuts muddiness. Resonance adds emphasis at the cutoff point. Combined with envelopes, filters become an expressive performance tool.
Next: controlling how sounds evolve over time from attack to release - the ADSR envelope.
Shape sounds with context
Starts lets you hear how filtered and unfiltered sounds work together in an arrangement.