Resonance · Browser Synthesis Laboratory · Bench 01
Resonance is a working synthesizer built from raw oscillators, running entirely in your browser. Power it on, play the keys, and watch each note travel through a live oscilloscope and spectrum analyser. Nothing here is recorded — every tone is computed the instant you ask for it.
▼ THE INSTRUMENT IS LIVE BELOW — PRESS POWER TO BEGIN
Play with your mouse, touch, or type A–L · black keys on W E T Y U O PTap the keys — sliding a held finger glides between notes
The Signal Path
Every note you play is born as bare voltage-style math and shaped on its way to the speaker. This is the exact chain running on this page — no samples, no audio files, no shortcuts. Follow a keypress from left to right.
Two oscillators start the note. B runs a few cents flat of A, and the slow beating between them is what turns a clinical tone into a living one.
Each voice is summed to a single line at conservative gain, leaving headroom so a full chord never clips the bus.
A resonant low-pass filter carves the top off the harmonic stack. Sweep the cutoff while holding a saw and you hear the harmonics leave one by one.
An exponential envelope opens in five milliseconds and closes at the release time you set. This is where a tone becomes a note.
A 2048-point analyser taps the bus without touching it — time domain to the scope, frequency domain to the bars.
The master bus meets your hardware at its native sample rate. From keypress to speaker in a few milliseconds.
The Modules
Resonance is built like a modular system: small circuits with one job each, patched together. These are the modules wired into the instrument above, with the values they run at.
The only stage that creates energy — everything after it can only remove or reshape. Four classic wave shapes are on the panel: sine is a single harmonic, triangle adds soft odd harmonics, saw carries the full series, and square hollows it to odd harmonics only.
RANGE C3–E4 · TUNING A4 = 440 Hz
A 12 dB-per-octave low-pass with a resonance peak at the cutoff. Push the Q past twelve and the filter begins to sing at its own corner frequency — the self-oscillation this lab is named for.
CUTOFF 100 Hz – 12 kHz · Q 0.5–18
Amplitude follows an exponential attack–release contour, the same curve a charging capacitor traces. A fast fixed attack keeps the keys percussive; the release slider decides how long each note hangs in the air.
ATTACK 5 ms FIXED · RELEASE 50 ms – 2.5 s
Oscillator B is deliberately mistuned against A by a handful of cents. The two waves drift in and out of phase, and the interference sweeps the timbre by itself — chorus with zero extra circuitry.
DETUNE 0–25 CENTS · DEFAULT 7
One FFT node feeds both displays. The scope draws 2048 amplitude samples with phosphor persistence, so bright traces decay the way they would on a real CRT. The spectrum draws the harmonic stack with peak-hold caps that fall under their own gravity.
FFT 2048 · SMOOTHING 0.8 · ~60 FPS
A single gain stage guards the exit. Voice levels are budgeted so that a full ten-finger chord sums below clipping, and the whole mix rides out at a comfortable listening level.
HEADROOM ≥ 6 dB · VOICES UNLIMITED
Philosophy
A sawtooth wave contains every harmonic at once — the fundamental, then each overtone above it, fading gently as they climb. Synthesis of this kind starts with that abundance and carves away. The filter is the sculptor's chisel: everything above the cutoff falls to the floor, and what remains is the tone you meant.
This is why the instrument above rewards slow hands. Hold one saw note and drag the cutoff down — you can hear the harmonics leave in order, top first, until only the fundamental hums. Push the resonance and the filter's own voice rises at the edge of the cut, ringing like a wet finger on glass. Two knobs, one note, an entire vocabulary.
Resonance exists to make that vocabulary visible. The scope shows you the shape your ears already know; the spectrum shows the arithmetic underneath it. When the picture and the sound click together — when you see a square wave hollow out as its even harmonics vanish — the theory stops being theory.
The oscilloscope has no opinion. It draws exactly what you played, which is why it is the most honest teacher in the room.