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How to use an auto filter

Gazillion Industries · September 14, 2026

A pad that never moves is wallpaper. Somebody walks past it for eight bars and nobody remembers the pattern. Put a filter on it that breathes and suddenly the wall is a window.

An auto filter is a filter whose cutoff moves on its own, usually driven by an LFO synced to tempo or by an envelope that follows the input level. Set the filter type and cutoff, choose how far and how fast it moves, add a little resonance so the movement is audible, and sync the rate to the beat. It adds motion and groove to pads, chords, drums and samples without writing any automation.

The short version

How an auto filter works

A filter removes frequencies above or below its cutoff. An auto filter moves that cutoff for you. In LFO mode, a low-frequency oscillator swings it up and down in a shape (sine for smooth, square for choppy, sample-and-hold for random steps) at a rate you set, usually in note values like quarter notes or bars. In envelope mode, the cutoff opens as the input gets louder and closes as it quiets, so the filter reacts to the performance.

Sidechain filtering

Point the envelope follower at a different track and the filter moves with that instead. Follow the kick and a pad's brightness ducks and returns with every hit, a softer, more tonal version of sidechain compression. Follow a vocal and the beat opens up when the rapper comes in. It's a way of making two parts react to each other without touching their levels.

How to use an auto filter

1. Put an auto filter on a pad, chord, sample or drum loop.
2. Pick a low-pass for warmth or a band-pass for a wah-like sweep.
3. Set the cutoff near the middle of where you want it to move.
4. Choose LFO mode, sync the rate to the tempo, and start with a slow value like one bar.
5. Raise the depth until you hear the movement, then back it off.
6. Add a little resonance so the sweep has a voice.
7. Try a faster rate or a stepped shape for rhythm.

F(ilter)12 has both: AUTO FILTER on a clock with swing, and SIDECHAIN that follows another signal. There's a demo on the page.

Groove, not just movement

A synced LFO moves in perfect time, which can sound mechanical against swung drums. If your auto filter offers swing or a grid, push its steps off the beat the same way the hats are swung, and the filter will sit in the pocket instead of marching over it. For one-time sweeps into a drop, automation is the better tool: see how to make a filter sweep.

Where it works

• Pads and chords: slow low-pass movement so a loop breathes.
• Drum loops: band-pass or high-pass at a rhythmic rate for variation.
• Lofi textures: gentle movement on a crushed sample (see how to make lofi beats).
• Bass: envelope mode for funky, touch-sensitive movement.

Questions people ask

What does an auto filter do in music?

It moves a filter's cutoff automatically, either in a repeating pattern from an LFO synced to tempo or in response to the input's level, adding motion to a sound without manual automation.

What is a sidechain filter?

A filter whose cutoff is controlled by a different signal, such as the kick, so one track's brightness moves in response to another. It creates a pumping or ducking effect that's more tonal than sidechain compression.

What's the difference between an auto filter and a filter sweep?

An auto filter repeats its movement automatically for as long as it runs. A filter sweep is usually a one-time move, written with automation, like a low-pass opening into a drop.

Stock plugins that do this

What F(ilter)12 does

F(ilter)12 can move its filter two ways, one at a time. AUTO FILTER hands it to a clock: a shape, a division, a grid, and SWING to push it off the grid. SIDECHAIN hands it to a signal instead: what it follows, what it hears, which way it travels, how far, and how eagerly it makes up its mind. The filter itself has five shapes and eight resonance shapes that travel with the knob.

Same pad, same eight bars. Now people look out the window.

Keep reading

• How to make a filter sweep — High-pass and low-pass builds, automation curve, resonance, and what to sweep.
• How to make lofi beats — Tempo, chords, swung drums, crush, noise, wobble and a gentle pump.
• How to make your beats sound fuller — Cover the frequency range, layer and double, add saturation, width and space.

Gazillion Industries LLC · reading material