The Air Theremin is a web application that produces a theremin sound when users move their hands in front of a webcam. Moving the hands apart changes volume, raising them changes pitch, and bringing the palms together silences the instrument. The same functionality is available on a phone by tilting the device, with left‑right motion adjusting volume and forward‑back motion adjusting pitch. A mouse can also control the instrument. Users can press a start button to calibrate the sensor to their grip. The application runs in any modern browser and requires only the device’s camera or motion sensors.