Play music with your hands
The camera is only requested when you press Enable camera, and frames never leave your browser. Keyboard mode needs no permission at all.
Gesture Synth Weld is a free browser instrument: your webcam tracks your hands, your hands play chords, and the performance comes back out as a standard .mid file you can open in any DAW. No install, no sign-up, and no webcam required if you would rather use the keyboard.
Every other browser gesture synth is a closed loop: you wave your hands, you hear a sound, and that is where it ends. Here the note events are captured while you record, then written out as a format-0 Standard MIDI File with real note-on and note-off pairs at 120 BPM.
.mid into Ableton, Logic, FL Studio, Reaper, Bitwig or GarageBand.Because notes that carry across a chord change are held rather than retriggered, the exported clip reads as musical phrasing instead of a wall of repeated one-frame notes.
No camera, blocked permission, or just not in the mood to be on video? Keyboard mode plays the same instrument with no camera prompt and no model download.
| Key | What it does |
|---|---|
| 1 – 7 | Scale degrees I – VII — hold to play, release to stop |
| [ / ] | Minor / major mode |
| 8 9 0 - | Triad · 1st inversion · 7th · 9th |
| Shift | Octave down |
| ↑ / ↓ | Volume sweep (hold) |
| ← / → | Filter sweep (hold) |
| Space | Stop all notes |
| Fingers | Degree | Gesture | In A major |
|---|---|---|---|
| 1 | I | Any one finger | A |
| 2 | ii | Any two fingers | Bm |
| 3 | iii | Any three fingers | C♯m |
| 4 | IV | Any four fingers | D |
| 5 | V | All five fingers | E |
| VI | vi | Index + pinky only | F♯m |
| VII | vii° | Index + pinky + thumb | G♯dim |
| 0 | — | Fist | Mute |
Degrees follow real diatonic harmony rather than forcing every degree to a major triad — that is why a I–vi–IV–V sweep already sounds like a song.
| Movement | Controls |
|---|---|
| Fingers (1–4) | Triad → 1st inversion → 7th → 9th |
| Hand height | Volume |
| Wrist tilt | Filter sweep — right brighter, left darker |
| Thumb extended | Drop one octave |
Every other browser gesture synth ships a hardcoded table of major and minor triads, which caps the instrument at two sounds. Here each mode is stored as its raw semitone set and chords are generated by stacking thirds through that set, so the harmony is derived rather than looked up — and the chord name is read back from the intervals that actually came out.
| Mode | I – IV – V in C | Character |
|---|---|---|
| Major (Ionian) | C · F · G | Bright, resolved |
| Natural Minor | Cm · Fm · Gm | Dark, classic sad |
| Dorian | Cm · F · Gm | Minor with a major IV — funk, folk |
| Mixolydian | C · F · Gm | Major with a flat 7 — rock, blues-rock |
| Lydian | C · F♯° · G | Floating, film-score |
| Phrygian | Cm · Fm · G° | Spanish, metal |
| Harmonic Minor | Cm · Fm · G | Minor with a major V — the tense one |
| Major Pentatonic | C · G · A | Five notes, nothing can clash |
| Blues | Csus4 · G♭ · G | Six notes with the flat five |
Because the sevenths are generated too, a 7th chord comes out as
Cmaj7 in major and C7 in mixolydian without either being
written down anywhere.
With Scale + wrist tilt enabled, tilting your left wrist drops to the parallel darker mode over the same tonic — major↔minor, lydian↔phrygian, mixolydian↔dorian, pentatonic↔blues. On a two-mode instrument that control is a switch; across nine modes it becomes a performance gesture.
| Mode | Left hand | Right hand |
|---|---|---|
| Gesture | Scale degree I–VII, major/minor tilt | Chord richness, volume, filter, octave |
| Theremin | Height = volume | Height = pitch (C3–C6, logarithmic), tilt = filter |
| Piano | Fingers pick root / 3rd / 5th / octave / 9th | Triggers the note, height = volume |
Theremin pitch is mapped logarithmically, so the same hand movement gives the same musical interval anywhere in the range instead of cramming the top two octaves into the last inch.
40–240 BPM with tap tempo, four click sounds (click, wood, beep, hi-hat) and time signatures from 3/4 to 7/8. The downbeat is accented so you can hear the bar line. It routes past the instrument filter and reverb, so sweeping your wrist never smears the click — and it is audible in recordings, which is useful for layering takes and a nuisance otherwise, so turn it off before your final pass.
The synth engine is not a bank of bare oscillators. Each note is a pair of detuned oscillators with its own ADSR envelope, feeding a shared resonant lowpass, a generated-impulse convolution reverb and a limiter. Five presets — Warm Pad, Bright Synth, Retro Square, Ambient Pad and Harp Pluck — change the oscillator pair, envelope and reverb mix together rather than just swapping a waveform.
The arpeggiator sweeps chord tones as plucks at three speeds, and Auto Bass adds a sine root two octaves down that tracks your left hand.
Or skip it entirely — keyboard mode needs no camera.
Close anything else using it (Zoom, Teams, FaceTime — a camera serves one app at a time), then reload.
Hand tracking runs on the GPU via WebGL. Close other GPU-heavy apps, and plug in a laptop — some browsers throttle GPU work on battery. Chrome and Edge give the best MediaPipe performance.
Browsers block audio until you interact with the page, so the synth only starts after you click the start button. Check the system output device too.
Yes — record a take, then hit Export MIDI. It writes a format-0 .mid at 120 BPM with proper note-on/note-off pairs for every chord you held.
Yes. Keyboard mode plays the same instrument with keys 1–7 and needs no camera permission and no model download.
An instrument that turns webcam-tracked hand movement into notes — no MIDI controller, gloves or sensors involved.
No. Tracking runs on-device through MediaPipe compiled to WebAssembly. Frames never leave your browser and recordings are written to your own device.
Yes, with single-hand mode enabled in Settings — a phone's front camera rarely frames two hands well.
Chrome 90+, Edge 90+, Firefox 90+ and Safari 15+. Chrome or Edge give the smoothest tracking.