Synths, notes and chords
Filter cutoff and resonance, explained by ear
A filter removes part of a sound's frequencies. The cutoff sets where it starts cutting, and the resonance boosts the frequencies right at the cutoff, which adds a whistling or squelchy edge. A low-pass filter keeps the lows and cuts the highs, a high-pass filter does the opposite. EASY RAVE lets you hear all of this on its free synths in the browser.
What does a filter do?
Every sound is a mix of low and high frequencies. A filter lets some of them through and blocks the rest. Close a filter on a bright synth and it turns dark and muffled, like music heard through a wall. Open it and the brightness comes back.
Filters are the most played knob on a synthesizer, because moving one changes the character of a sound without changing the notes.
What is the cutoff?
The cutoff is the frequency where the filter starts cutting. On a low-pass filter:
- Cutoff high: almost everything passes. The sound is bright and full.
- Cutoff in the middle: the top end is gone. The sound is warmer, rounder.
- Cutoff low: only the deepest part is left. A thud, a hum.
In EASY RAVE the knob is called CUT OFF FREQ on the AC 303 bass and CUTOFF on the chord synth, the lead, the sampler and the drum machines.
What is resonance?
Resonance boosts the frequencies right at the cutoff point. A little resonance gives a sound more bite. A lot of resonance makes the filter whistle, and when you sweep the cutoff with high resonance you get the "wow" and the squelch of acid basslines.
The two knobs work as a pair: resonance is the shape of the edge, cutoff is where that edge sits. How to make acid house is basically a lesson in these two knobs.
Low-pass vs high-pass: what is the difference?
| Low-pass | High-pass | |
|---|---|---|
| Keeps | The lows | The highs |
| Removes | The highs | The lows |
| Sounds like | Muffled, under water, far away | Thin, tinny, like a phone speaker |
| Classic use | Warming a synth, a breakdown that sinks | Builds and risers before a drop |
In EASY RAVE's LIVE FX bar, the LO PASS and HI PASS pads put these two filters over the whole mix. Hold LO PASS and the track sinks under water; hold HI PASS and the low end drains away, which builds tension before a drop. Let go and the full sound slams back. Live effects shows how to use them in a performance.
What is envelope modulation?
On the AC 303, each note can open the filter by itself and let it fall closed again. That automatic movement is set by 2 knobs:
- ENV MOD: how far each note opens the filter.
- DECAY: how fast it falls back.
With ENV MOD up, every note "talks". Combine it with ACCENT, which opens the filter further on accented steps, and the line gets its rubbery bounce without you touching the cutoff at all.
On POLY-6 and THERE LEAD, an LFO knob does something similar on a slow cycle: it sweeps the filter up and down on its own, for a wobble.
How do you sweep a filter by hand in EASY RAVE?
You can drag any knob, but there is a faster way while the music plays. Hold a key anywhere and turn the mouse wheel:
| Hold | Sweeps the cutoff of |
|---|---|
| Z | BASS (AC 303) |
| X | CHORDS (POLY-6) |
| C | LEAD (THERE LEAD) |
| V | SAMPLER (SAMPLE KING) |
Hold several at once and the wheel sweeps them together. To keep a sweep, open AUTO in the transport and press REC AUTOMATION, then make the move: EASY RAVE plays it back on every pass. These keys can be changed in the shortcut map (press ?).
Things to try
- On AC 303, set RESONANCE to about three quarters and sweep CUT OFF FREQ slowly from bottom to top. Listen for the moment the bass starts to squelch.
- On POLY-6, turn CUTOFF down until the chords sound warm, then raise LFO for a slow wobble.
- While the whole track plays, hold HI PASS for 4 bars, then let go on the first beat of a bar.
- On a drum machine, lower CUTOFF to push the kit into the background during a breakdown.
Frequently asked questions
What is the difference between cutoff and resonance?
Cutoff sets the frequency where the filter starts removing sound. Resonance boosts the frequencies right at that point. Cutoff changes how bright the sound is, resonance changes how sharp and whistling the edge of the filter sounds.
Why does my synth sound muffled?
The filter cutoff is probably low, so a low-pass filter is removing the high frequencies. Turn the cutoff up to brighten it. In EASY RAVE, also check that the LO PASS pad in the LIVE FX bar is not pinned on.
What does a high-pass filter do in music?
A high-pass filter removes the low frequencies and keeps the highs. Producers sweep one over the whole mix before a drop to build tension, then switch it off so the bass and kick return with full impact.