Gesture Synth Weld is a free, browser-based hand gesture music synthesizer. Your left hand picks the chord, your right hand shapes the sound — no downloads, no hardware, no accounts. This is the official guide: every gesture, mapped.
Click "Enable Camera" and grant permission. Video stays on your device — nothing is uploaded.
1–5 fingers play scale degrees I–V. Special combos below reach VI and VII.
Both hands must be visible for sound. Raise your right hand for volume.
Press Record for up to 120 seconds, then download — or share straight to apps on mobile.
Watch it play: the four moves cycle on their own — or tap the dots — each step is one gesture you already read above.
Left hand: 1 finger (I) · Right hand: raised for volume
Left hand: 4 fingers (IV) — harmony moves, right hand stays
Left fist = mute. Open the hand and the chord comes back
Keyboard mode: keys 1–7 play I–VII, no webcam needed
Defaults out of the box: key of A · Major locked · fixed Major-Triad style. Change key in the toolbar, everything else in Settings.
Each finger count is a different scale degree. Examples in A Major:
| Fingers | Degree | Gesture | In A Major |
|---|---|---|---|
| 1 | I | Any 1 finger raised | A |
| 2 | ii | Any 2 fingers (not the VI combo) | Bm |
| 3 | iii | Any 3 fingers (not the VII combo) | C#m |
| 4 | IV | Any 4 fingers raised | D |
| 5 | V | All 5 fingers raised | E |
| Special | vi | Index + Pinky ONLY (middle / ring / thumb down) | F#m |
| Special | vii° | Index + Pinky + Thumb ONLY (middle / ring down) | G#dim |
| 0 (fist) | — | All fingers curled | Mute — resumes when fingers return |
By default the mode is locked to Major ("Scale notes only"). Switch to Scale+Tilt in Settings and your left wrist becomes the switch: tilt left = minor, tilt right = major. The toolbar key selector (C–B) transposes everything.
In Finger Layout mode, finger count sets chord thickness:
| Fingers | Major | Minor |
|---|---|---|
| 1 | Major Triad | Minor Triad |
| 2 | Major 1st Inversion | Minor 1st Inversion |
| 3 | Major 7th | Minor 7th |
| 4 | Major 9th | Minor 9th |
The default is Fixed Chord Style (Major Triad) — the right hand then controls only volume and tone. Or lock any of 8 styles in Settings: Major Triad · Major 1st Inv · Minor Triad · Diminished · Sus2 · Sus4 · Major 7th · Dominant 7th.
Right-hand height = pitch (C3→C6), left-hand height = volume. Continuous gliding, no chords.
Left-hand finger count picks the note (root / 3rd / 5th / octave / 9th); right hand triggers it.
Desktop only. 1–7 degrees (hold to play) · [ / ] minor/major · 8/9/0/- style · Shift octave down · ↑/↓ volume · ←/→ filter · Space stop. Recording is audio-only.
Worth knowing: Arpeggiator (Off/Slow/Normal/Fast) sweeps chord notes like a harp · Auto Bass adds a root note two octaves down with its own volume · Metronome (BPM 40–240, several time signatures — audible in recordings when on).
You don't need sheet music. This instrument plays chords by scale degree, so most songs reduce to a short loop of left-hand shapes: show 1–5 fingers for degrees I–V, index+pinky for VI, index+pinky+thumb for VII — and tilt your wrist for minor chords. The shapes work in any key, so learn a loop and you can jam along.
Left hand: 1 · 5 · 6 (tilt) · 4 — one wrist tilt on the vi is the whole trick. Heard in: Let It Be · With or Without You · Someone Like You.
Left hand: 6 (tilt) · 4 · 1 · 5 — same four chords, minor first. Heard in: Numb · Grenade · countless movie trailers.
Left hand: 1 · 6 (tilt) · 4 · 5 — the slow-dance loop. Heard in: Stand By Me · Every Breath You Take · Duke of Earl.
Left hand: 2 (tilt) · 5 · 1 — where every jazz standard lands. Right hand: add fingers for 7th/9th voicings for instant jazz color.
Left hand: 1 (tilt) · 7 · 6 · 5 — a descending staircase, the V landing major for that flamenco pull. Heard in: Hit the Road Jack.
Practice tip: turn on the metronome (BPM 40–240) to keep time and auto bass to fill the low end — both are audible in recordings. Prefer melodies over chords? Switch to Mono Piano.
Press Record: a 3-2-1 countdown, up to 120 seconds, a 3-2-1 wrap-up before it stops. Capture audio only, full video (camera + neon skeleton), or skeleton animation (privacy-friendly, no camera feed). Aspect ratios 9:16 / 16:9 / 1:1 for TikTok, YouTube, Instagram.
Sing along: enable the mic to sing over your chords, then download — or share straight to apps on mobile. Finished recordings also auto-save to My recordings in your browser, so your music is there when you come back.
Yes — free to play and record, no sign-up. MIT-licensed open source (GitHub).
No — Keyboard mode (desktop) plays the synth with physical keys only: no permission, no model download. On a phone? There is no app to install — the URL is the app.
Chrome 90+, Edge 90+, Firefox 90+, Safari 15+. Chrome or Edge recommended for the smoothest hand tracking.
Never — hand tracking runs locally on your device; the camera feed leaves nothing behind.
Most songs built on common chord progressions — the five loops above (I–V–vi–IV, ii–V–I and friends) cover a huge slice of pop, rock and jazz. Learn one loop and you can jam along to a surprising number of tracks.
Gesture Synth Weld is this site's two-hand instrument — left hand harmony, right hand expression — with 3 modes, arpeggiator, auto bass and built-in recording. Not a hardware glove, not a DAW plugin. New to the category? Start with what a gesture synth is.
Enough reading — your hands already know what to do.
▶ Open Gesture Synth Weld and playGesture Synth Weld — official tutorial. Play · Gesture Synth · About · Privacy · Terms · Contact · MIT License · Hosted Pro version: gesturesynthweld.app. Not affiliated with third-party tutorial sites using our name.
Hand icons: Sannita + MichaelFrey via Wikimedia Commons (CC BY-SA 3.0), OpenMoji (CC BY-SA 4.0).