The PalmDriver  (formerly TwinTowers) is an electronic device based on IR technology which consists of 8 sets of 4 sensing elements arranged as the vertical edges of a square-based parallelepiped.
At the time (1995) the first prototype was realized, we used only two sets of elements so that the shape of the beams reminded the profile of the “late” TwinTowers in New York to us.
The measurements of distance of the different zones of the hands’ palm are performed by the amount of reflected light captured by the receivers and are quite accurate in respect to the irregularity and color of the hands’ palms.
The PalmDriver  is stable and responsive; as a consequence, sounds generated by the computer evoke on the performer the sensation of “touching the sound”.    video

Image processing technology has been used for realizing Handel System: a CCD camera is connected to a video grabber card; the digital image is then analyzed as the reconstructed image consisting of those pixels whose luminance is greater than a predefined threshold and color.
Panes are defined dynamically; x-y position and dimensions of the frames inside panes are detected.

see paper : Handel, a free-hands gesture recognition system (CMMR2004 - Springer)

On the basis of Handel, the Imaginary Piano has been realized: here a single rectangle - with a small thickness, as long as the horizontal dimension of the video capture area - is defined at the height where the keyboard usually lies.
When a finger, or a hand, crosses that strip downward, the systems reports proper information regarding the “key number” and a specific message is issued accordingly to “where” and  "how fast" the rectangle has been crossed. Information is used for controlling an algorithmic compositions rather than for playing scored music. video