High-pass filter

A high-pass filter is the mirror image of a low-pass filter: it keeps the top of a sound and removes the bottom, starting at the cutoff frequency. Raise the cutoff slowly on a full synth chord and the weight drains out first. The bass note fades, then the body of the chord, until only a thin, fizzy top is left, like a song coming out of a phone speaker.

On synths it is less common than low-pass. In sound design it keeps a pad or lead light, and a little resonance at the cutoff adds a thin, nasal peak. In dance music it drives the build-up: a high-pass on a synth part, or on the whole track, sweeps slowly upward over the bars before a drop, so the music thins out and the drop lands with the full low end back.

Its everyday job is in mixing, where EQ plugins label it HPF or Low Cut. Pads, guitars, vocals and chord parts often carry low-frequency energy that muddies the bass and kick drum. A high-pass around 100 to 150 Hz on a pad or a strummed chord part clears that space, and in a full mix you rarely miss what it removed. Set it too high and the part turns small and tinny, so sweep the cutoff up until you hear the part change, then back it off a little.

The filter cutoff and resonance guide compares high-pass, low-pass and band-pass side by side, and how to make a synth sound bigger uses a high-pass to keep a supersaw out of the bass’s way. In Gelato Synth, choose High (from Low, Band or High pass) on the Filter page.