How to Play Gesture Synth
A step-by-step tutorial for playing chords with your hands in front of a webcam. No music theory needed, and your first chord takes under a minute.
This guide shows you how to play gesture synth chords with Gestune, a free instrument that runs in your browser. Your left hand picks the chord and your right hand shapes how it sounds.
Play your first chord in under a minute
Follow these steps once and you will hear a chord change under your own hands.
- 1
Open the instrument
Go to the Gestune home page in desktop Chrome or Edge if you can. Safari works too, and so do phones, just a little less smoothly.
- 2
Press Start Playing
Sound starts first, then your browser asks for camera access. Allow it. If you would rather not use the camera, the keyboard and on-screen pads work fully on their own.
- 3
Raise your left hand with one finger up
Hold your index finger up on the left side of the screen. You will hear chord I, the home chord of the key. In C major that is C.
- 4
Change the number of fingers
Show two, three or four fingers, then open your whole hand. Each shape plays a different chord. Make a fist to stop the sound.
- 5
Add your right hand
Raise your right hand on the right side of the screen. Move it up to get louder and down to get quieter. You are now playing with both hands.
Set up your camera, light and space
Good tracking makes everything else easier. A few minutes of setup saves a lot of frustration later.
Camera and distance
Any laptop camera or USB webcam is fine. Sit about an arm’s length away so both hands fit in the frame with room to spare.
Light and background
Face a window or lamp so your hands are lit from the front. A plain wall behind you beats a busy shelf.
Browser and privacy
Hand tracking uses Google’s MediaPipe hand model and runs on your device. Your camera video is never uploaded or stored on a server. On a phone, turn it sideways so both hands fit side by side.
Gesture synth chords: the left-hand signs
Your left hand is the chord hand. Each shape plays one of the seven chords of the current key. The table shows what each sign plays in C major.
| Left hand | Shape | Plays |
|---|---|---|
| Index finger up | I (C in C major) | |
| Index + middle | ii (Dm in C major) | |
| Index + middle + ring | iii (Em in C major) | |
| Four fingers, thumb tucked | IV (F in C major) | |
| Open hand (all five) | V (G in C major) | |
| Index + pinky (rock sign) | vi (Am in C major) | |
| Thumb + index + pinky | vii° (Bdim in C major) | |
| Fist or hand out of view | Silence | |
| Tilt left past about 20° | Force minor (e.g. IV → iv) | |
| Tilt right past about 20° | Force major (e.g. iii → III) |
What the chord numbers mean
Numbers and Roman numerals in plain words
Every key has seven notes. You can build a chord on each one, so every key has seven chords. Musicians number them I to VII with Roman numerals. Chord I is home, the chord a song usually starts and ends on. Chord V pulls strongly back toward home.
Uppercase numerals like IV mean a major chord, which tends to sound bright. Lowercase numerals like vi mean minor, which tends to sound darker or sadder. The finger count on your left hand is simply the chord number, with special signs for VI and VII.
The natural chord of the key
When your hand is upright, you get the chord that naturally belongs to the key. In C major those are C, Dm, Em, F, G, Am and Bdim. You never have to remember which is major or minor. Pick a number and the right chord comes out.
Change the key and the same signs play the chords of the new key. There are 12 keys, in major or natural minor.
Tilt for major or minor
Many songs borrow a chord from outside the key. To play one, tilt your left hand. Tilt it left past about 20 degrees to force a minor chord. Tilt it right past about 20 degrees to force a major chord. Hold it upright to go back to the natural chord.
Here is a real example. Creep by Radiohead is in G major and uses G, B, C and Cm. G is chord I with one finger. B is chord III, which is normally Bm in G, so you show three fingers and tilt right. C is chord IV with four fingers. Cm is the same four fingers tilted left. Four chords, two tilts, one famous song.
The expression hand: volume, tone and voicing
Your right hand shapes the sound of whatever chord your left hand is holding.
| Right hand | Shape | Does |
|---|---|---|
| 1 finger | Triad (closest inversion when Smooth chord changes is on) | |
| 2 fingers | First inversion | |
| 3 fingers | Second inversion | |
| 4 fingers | Seventh chord | |
| Thumb out | One octave lower | |
| Hand height | Volume (higher = louder) | |
| Hand tilt | Tone (darker ↔ brighter) |
Inversions and sevenths, simply explained
Volume and tone
Raise your right hand to get louder, lower it to get quieter, and tilt it to make the sound darker or brighter. If it leaves the frame, the last settings are kept.
Inversions
A chord is three notes stacked up. An inversion plays the same three notes with a different one at the bottom. It is still the same chord, it just sits higher or lower and feels a little different. Two fingers give the first inversion, three give the second.
Seventh chords and the low octave
Four fingers on the right hand add a fourth note, turning the chord into a seventh chord. Sevenths sound richer and jazzier. Stick your thumb out to drop everything one octave lower for a deeper sound.
Smooth chord changes and steady tracking
Smooth chord changes
On by default, this picks the closest inversion for each new chord, so the notes glide instead of jumping. Musicians call this voice leading. Turn it off to choose every inversion yourself.
Response setting and flicker
A shape has to hold for a few frames before the chord changes, so a shaky hand does not flicker between chords. A brief loss of tracking under 0.2 seconds does not cut the sound either. In Settings, Response has three choices: Fast, Balanced and Stable. Pick Stable if chords still flicker, or Fast if changes feel slow.
Still jumpy? Add light, move back a little and spread your fingers. Turn on Show hand skeleton to see what the camera sees.
Play with the keyboard instead
No camera, or just want to practice the changes? Every chord also works from your keyboard or the on-screen pads, which support multi-touch.
| Key | Action |
|---|---|
| 1 – 7 | Play chords I – VII (hold to sound, release to stop) |
| Shift (hold) | Flip the chord between major and minor |
| Q | Triad |
| W | First inversion |
| E | Second inversion |
| R | Seventh chord |
Practice with real songs
Open the Learn a song panel above the camera. Loading a song switches to its key and shows the hand sign for the current and next chord. There are no lyrics, just chords.
Follow mode
The song waits until you play the right chord, then moves on. Perfect for learning the shapes at your own pace.
Play-along mode
Four count-in clicks, then the song runs at its real tempo. Chords played on time turn green, and you get a score at the end.
Let It Be by The Beatles
A slow song in C major with four clear chords. A great first song.
All songs
Browse every song with its key, tempo and chord chart.
Left-handed players
Prefer to pick chords with your right hand? Open Settings and turn on Swap hands. Your right hand becomes the chord hand and your left hand controls volume, tone and voicing. Hands are assigned by which half of the screen they are in, and the video is mirrored like a mirror, so your left hand appears on the left.
Once you are comfortable, try recording a clip of yourself playing to share, or switch to the webcam theremin for a completely different way to play.
Questions about playing
Do I need to know music theory?
No. Hold up a number of fingers and the matching chord plays in the right key. The tutorial and the song panel show you which sign to use.
Why does nothing happen when I raise my hand?
Check that you allowed camera access and that your hand is fully in frame. If the camera is blocked, the app shows steps for Chrome, Edge and Safari, or you can play with the keyboard instead.
Which hand plays the chords?
By default the hand on the left half of the screen plays chords and the hand on the right controls the sound. Turn on Swap hands in Settings to flip them.
How do I stop the sound?
Make a fist with your chord hand or move it out of view. Releasing the key does the same on the keyboard.
Why do my chords flicker?
Usually the light is low or your fingers are hard to see. Add light, move back a little and set Response to Stable in Settings.
What is the difference between a triad and a seventh chord?
A triad has three notes. A seventh chord adds a fourth note on top, which sounds fuller and a bit jazzier. Show four fingers on your right hand to play one.
Can I change the key or the sound?
Yes. Choose any of 12 keys in major or minor, and pick from Warm Pad, Glass Keys, Analog Saw or Chord Harp.
Can I see the tutorial again?
Yes. Press the Help button to replay the four-step tutorial at any time.
Ready to try the hand signs? Your first chord is one finger away.
Open the instrument