Gesture Synth Not Working? Camera, Sound and Tracking Fixes

Short answer: most gesture synth problems are one of five things: the camera is blocked, the hand is not detected, there is no sound, the frame rate is low, or the browser is unsupported. Find your symptom below; each fix takes under a minute. If nothing works, switch Input to Mouse / touch or Keyboard and keep playing.

Camera blocked or not listed

• Prompt was denied: click the lock or camera icon in the address bar, set Camera to Allow, reload, press Begin.
• No prompt at all: the page must be on HTTPS. HandSynth always is; if you opened a copy from a file or plain HTTP, the browser hides the camera.
• "Camera in use": another app (Zoom, Teams, OBS, a virtual camera) holds the device. Quit it or pick a different camera in the browser's site settings.
• macOS: System Settings, Privacy and Security, Camera: enable your browser.
• Windows: Settings, Privacy and security, Camera: allow desktop apps and your browser.
• No camera on this machine: choose Mouse / touch or Keyboard as the input. The instrument is the same.

Hands not detected or the chord flickers

• Light in front, not behind. A window behind you turns your hand into a silhouette. Face the light.
• Palm to the camera. An edge-on hand loses landmarks. Keep fingers spread and pointing up.
• Distance. Sit an arm's length away so the hand fills about a fifth of the frame.
• Busy background. A plain wall behind your hand helps in low light.
• Wrong hand label. If the chord hand is treated as the expression hand, pull both hands out of frame and reintroduce them one at a time.
• Finger count off by one. The thumb only counts when it is clearly out to the side. Tuck it in for chords I to IV and open it wide for V.

No sound

• Press Begin again. Browsers only start audio after a click or tap; a page reload resets that.
• iPhone silent switch. Flip the switch on the side of the phone; iOS mutes web audio in silent mode.
• Bluetooth headphones. Expect 100 to 250 ms of extra latency. Use wired headphones or the speakers when timing matters.
• Volume hand too low. In chord mode, the right hand near the bottom of the frame is nearly silent. Raise it or use one hand only.
• System output. Check the browser is not muted in the OS mixer and that the right output device is selected.

Low frame rate or laggy tracking

• Close other camera tabs and video calls; the webcam can only feed one at full rate.
• Use Chrome or Edge. They run the tracker on the GPU. Firefox and Safari fall back to the CPU and can drop to 10 to 15 fps on older laptops.
• Plug in. Laptops on battery throttle the GPU.
• Watch the numbers. The stage shows fps and tracking time. Under 15 fps, the Strings sound hides jitter; under 8 fps, switch to Mouse / touch.

Browser support

• Chrome 100+, Edge 100+: everything, including MIDI out.
• Firefox 115+: everything except MIDI out; tracking is CPU only.
• Safari 17+ on Mac: works; note snap and recording work; MIDI out is not available.
• iOS Safari: camera and audio work after a tap; tracking may be slow on phones older than 2021, so the touch fallback is offered. See the mobile guide.
• In-app browsers (Instagram, TikTok, Facebook) often block the camera. Open the page in the real browser.

Recording problems

• No file downloads: the browser may block automatic downloads; allow them for this site.
• File is .webm or .m4a instead of .wav: the browser could not decode its own recording for conversion; the file still plays in any media player.

MIDI out shows no ports

On macOS open Audio MIDI Setup, Window, Show MIDI Studio, double-click IAC Driver and tick "Device is online". On Windows install loopMIDI and create a port. Reload the page and press MIDI out again. Web MIDI only exists in Chrome and Edge.

Still stuck? Write to us from the about page with your browser, device and what the status line on the stage says. For the basics of the controls, go back to how to play.