The theremin is an early electronic musical instrument controlled without physical contact by the thereminist (performer). It is named after the Westernized name of its Russian inventor, Léon Theremin, who patented the device in 1928.
The instrument's controlling section usually consists of two metal antennas that sense the relative position of the thereminist's hands and control oscillators for frequency with one hand, and amplitude (volume) with the other. The electric signals from the theremin are amplified and sent to a loudspeaker.
More information about the theremin can be found here and an example of how the theremin is play here.
This virtual theremin is created using computer vision and Web Audio API.
The web application will recognize the hands of the user and it will start making sound. Moving the left arm up and down the user will turn up or turn down the volume and moving the right arm up or down the user will increase or decrease the pitch.