Drums

Hi-Hat

A self-contained hi-hat voice: six inharmonic square oscillators bandpassed and high-passed, with separate closed and open triggers.

Try one in your browser →

What is a Hi-Hat?

A hi-hat voice synthesizes the sound of a closed or open hi-hat from scratch. This sound is unusual to synthesize because real hi-hats are physically chaotic - two metal cymbals clashing - and the resulting sound is inharmonic, meaning its partials do not line up with any neat integer ratio. White noise gets you close, but it sounds too even and too 'noise-like'. Real hat has a metallic shimmer that pure noise lacks, and that shimmer is what every TR-style hi-hat circuit is designed to fake.

The trick the Roland TR-808 HH invented and TR-606 HH refined is brilliant in its simplicity: take six square-wave oscillators and tune them to deliberately inharmonic frequencies - the canonical 808 set is 205, 304, 370, 523, 540, 800 Hz - and sum them. Each oscillator on its own is a bright, hollow tone; six of them at non-integer-related frequencies stacked together produce a dense, pitched-but-not-tonal noise spectrum. It does not sound like noise and it does not sound like a chord - it sounds like metal.

That stack is then run through bandpass and highpass filters to discard the low end and isolate the bright partials, and through two amplitude envelopes: a short one for closed hat (15-40 ms) and a long one for open hat (200-500 ms). The two envelopes are usually triggered by separate gate inputs, and the closed hit chokes any open hat that is still ringing - just like a real player closing the pedal mutes the cymbals. Same six oscillators, same filters, two trigger inputs, two decay times. That is the entire 808 hat circuit, and it has not been improved on in 40 years.

Our Hi-Hat

Webrack's Hi-Hat keeps the architecture that defines the sound. The metallic-noise core is the canonical six square oscillators at the original 808 frequencies (205, 304, 370, 523, 540, 800 Hz), summed and run through an SVF bandpass (the Color knob sets its center) and an SVF highpass (the Tone knob sets its cutoff). Two amplitude envelopes - one fast, one slow - share the oscillator-and-filter chain, with hard choke when closed fires.

Two trigger inputs (CH and OH), seven knobs. Color sets the bandpass center, CH.Dcy and OH.Dcy are the two decay times, Metal slightly detunes the oscillators for grittier inharmonic character, Tone sets the highpass cutoff, and Drive adds tanh saturation for crunchy lo-fi hats. The Acc input boosts level on emphasized hits.

Architecturally a true sibling of the 808/606 hi-hat circuits, with no glitching and rock-solid timing under any trigger pattern. It will not be a perfect analog match, but the six-oscillator-plus-dual-filter topology is the actual reason hi-hats sound like hi-hats, and we keep it intact.

In a patch

Hi-hats define the subdivision of a pattern - usually they sit on every eighth or sixteenth note, which is faster than the kick or snare and provides the rhythmic momentum. The classic patch is two outputs from an Euclidean or step sequencer: one drives the closed-hat input on the eighths, the other drives the open-hat input on a few sparser positions for accent. The choke behavior takes care of the rest.

A few patching habits worth keeping: hi-hats benefit from panning slightly off-center in stereo mixes to create space - send the output to a Stereo Mixer with the pan offset. Send the gate output of Bernoulli into the closed-hat input for organic, slightly randomized hat patterns. And feeding an LFO into the Color or Tone CV (if available) shifts the hat's character over time, which is a cheap way to make a static hat pattern feel alive.

Inputs

CH (gate) — Closed-hat trigger. Each rising edge fires a short closed hi-hat AND chokes any active open hat in progress.
OH (gate) — Open-hat trigger. Each rising edge fires a long open hi-hat. Will be choked by the next closed-hat trigger.
Acc (cv) — Accent CV (0-10V). Boosts level for emphasized hits on either trigger.

Outputs

Out (audio) — Audio output. Mixes both closed and open hi-hats.
Env (cv) — Envelope follower of the hi-hat amplitude. Useful for sidechain ducking or modulating other voices.

Controls

Color — Base frequency multiplier for the 6 oscillator bank, 4-12 kHz. Lower for darker hats; higher for bright shimmer.
CH.Dcy — Closed hat decay, 5-100 ms. 15-25 ms for tight closed hats; 40-80 ms for slightly longer pedal-style.
OH.Dcy — Open hat decay, 100-1000 ms. 200-300 ms for typical open hats; 500+ ms for long sustaining hats.
Drive — Tanh saturation of the noise spectrum. Adds crunch and weight - useful for industrial textures.
Metal — Adds inharmonic overtones to the oscillator bank. 0 = clean metallic character; 1 = more clangy, bell-like noise.
Tone — High-pass filter cutoff, 6-16 kHz. Higher = thinner, brighter; lower = fuller, more body.
Gain — Output level, 0-1.

Inspired by

The 808 hi-hat trick is a small piece of synthesis genius: six square-wave oscillators tuned to deliberately inharmonic frequencies are summed to create a dense, pitched-but-not-tonal noise spectrum, then sculpted by bandpass and highpass filters until only the bright shimmer is left. We use the canonical six-frequency stack (around 205, 304, 370, 523, 540, 800 Hz) into an SVF bandpass and SVF highpass, with two amplitude envelopes for closed and open hat plus authentic choke - a closed hit silences any open hat that is still ringing.

Roland TR-808 HH
Roland TR-606 HH

← Back to all modules