This half-pendulum half-harp musical instrument is the creation of New York based interactive design company, Pattern Studio. Dubbed "The Gravity Harp," it was commissioned by Icelandic musician Bjork for her recent Biophilia tour. The innovative device features four robotic pendulums, each housing an eleven string harp. Hanging 20 feet above ground, the pendulums slowly swing back and forth whilst communicating with a control computer using an RS485 network. In order to maintain an even sequence of notes, each pendulum swings 90 degrees out of phase with its neighbor and is controlled by a motor attached at the top.

The harp can play pre-programmed or live melodies by using control software written in Python, which sends out commands to each pendulum to keep them synchronized and playing the correct notes. An artist can therefore "play" the instrument live by entering the notes into the computer in real time, and as with a classical instrument, this also permits the musician to perform an improvised piece of music.

The Gravity Harp was so large that Pattern Studio had to hire a warehouse space in Brooklyn featuring 30 foot (9 meter) ceilings to house it.

You can see and hear it in action in the video below.