MATRIXSYNTH: Lyratron

Currently seeking funding on Kickstarter.

Note there was also an AirHarp project by Adam Somers based on Leap Motion technology.

The Lyratron AriHarp is by Peter DeSimone. Some details (note the different physical designs - one more video below):

"The AirHarp is an electronic musical instrument invented by Peter DeSimone that responds to hand gestures, allowing the musician to "strum" invisible harp strings in the air. Rather than play scales like a normal harp, the AirHarp is designed to play chords, like an autoharp. The musician selects the desired chord by pressing a combination of buttons with the hand that's holding the instrument, while the empty hand is free to strum chords on a beam of ultrasound.

The AirHarp Lira is the latest in a series of AirHarp models designed and built by Peter DeSimone and Erik Jacobson. It's a MIDI controller instrument, so it doesn't make sound on its own. Rather, it sends messages to a computer, synthesizer or other device, which in turn creates the actual sound. Backers are encouraged to familiarize themselves with software synthesis and the use of MIDI controller instruments prior to purchasing an AirHarp Lira. However we will do our best to assist any customers who have issues setting up software synthesis. You will need a MIDI cable for use with a keyboard synthesizer, or a MIDI to USB converter cable for use with a computer. Modern Macintosh computers come with GarageBand pre-installed. Several free softsynth or "VST" host packages exist for Windows, including Cantabile Lite and SAVIHost...

The AirHarp Lira is powered by a single AA battery. To power certain onboard systems including the Maxbotix LV-EZ1 ultrasonic rangefinder, the battery's 1.5 volts is stepped up to 5 volts using a dedicated circuit. Back-bias protection is provided by a diode, and two electrolytic capacitors perform decoupling of power supply noise. An ATmega328 microcontroller clocked at 16 megahertz via a ceramic resonator decodes user input and encodes MIDI output messages. The AirHarp Lira is programmable via a standard FTDI serial interface using the Arduino IDE. Its firmware was written entirely in Arduino C. It is an Arduino-compatible microcontroller platform with rows of empty I/O pin holes on either side of the chip, specifically to encourage hacking. Early AirHarps used actual Arduinos; the AirHarp Lira uses a naked chip to save money (doing so saves about $25 per harp!)"