This cool music instrument is built by SthepenHobley based on Arduino. This harp doesn’t make sound itself but generates a stream of MIDI data to drive an audio synthesizer. In other word, Laser Harp works as MIDI controller. The way it works is simple, when the player’s hand interrupts the laser beam Theremin, the photocell sensor send signal to Arduino microcontroller to send a MIDI ‘Note On’ message. Additionally, GP2D120 IR range sensors reads the position of the hand and prompt the MCU to send another MIDI controller messages that change the sound’s qualities (pitch).
This harp is limited to 6 beams since Arduino has 6 analog inputs. But, you can expand it using multiplexer or bigger micro like ATmegaXX. See video below to watch arduino laser harp in action.