What is Laser harp ?

A laser harp is an electronic musical instrument consisting of several laser beams to be blocked, in analogy with the plucking of the strings of a harp, in order to produce sounds. It was popularized by Jean Michel Jarre, and has been a high profile feature of almost all his concerts since 1981. In recent times, a very similar version has also been used in concerts by British electronic musician Little Boots.

It has subsequently been used in a number of different designs, including a MIDI version invented by Philippe Guerre, and a recent one created by Yan Terrien. They have also been used in public art installations such as those created by Jen Lewin on display at Lincoln Center in 2000 and Burning Man 2005.

Design

Unframed style, also known as "Infinite Beam" laser harps:

This style of laser harp is generally built using a single laser, splitting its beam into an array of beams in parallel or fan arrangement. Playing the actual sound is usually handled by connecting the laser harp to a synthesizer, sampler or computer.

This frameless design is somewhat more elaborate than the Framed style, relying on the light being reflected back to a single photodiode. The fan of laser beams is actually a single beam being scanned into a fan pattern. By matching the timing of the reflected beam, it can be determined which of the beams is being blocked and which note needs to be heard. Alternative designs make use of multiple lasers; in these designs, each laser can be independently controlled (pulsed on and off) to simulate playback of prerecorded notes.

In order to generate more control data, such as a continuous range of values like those found in many MIDI controllers, several approaches are available: 1) using an infrared or ultrasonic rangefinder attached to the instrument, such that the position of the hand "plucking the string" is determined; 2) using a laser-based rangefinder to determine the distance from the hand to the laser's starting or ending point (and possibly using this laser itself as the string), a variation on this is using the intensity of the sensor signal itself; and 3) using a camera to track the position and motion of the laser dot on the hand, or the length of the exposed beam if visible, then calculating a continuous value based upon a reference. Stephen Hobley uses this method by exploiting the camera functionality of the Wii Remote.

Other possibilities no doubt exist. Each of these possibilities poses particular challenges and costs, though the first one is relatively inexpensive and straightforward to implement, and can use the same microcontroller which drives the lasers and reads the detectors.

The advantage of using a dedicated sensor mechanism is that the instrument can be self-contained, as opposed to requiring a computer to control it when an ILDA interface and USB camera are used. On the other hand, the PC-based approach offers more flexibility and can be constructed using mostly off-the-shelf hardware.

Unframed laser harps benefit from the use of higher-power lasers, as they facilitate easier detection by the sensor system. As the sensor is exposed to all ambient light, it can get swamped out by stage lighting behind the artist if the sensitivity is too high. Companies Kromlaser. And Prolight that makes Laser Harp controller, successfully avoid this problem, with ambient light and made sensor almost light independent. The use of (white or light-coloured) gloves improves the instrument's performance by allowing more light to scatter off the player's hands and therefore provide the sensor with a higher signal-to-noise ratio with respect to ambient light. Furthermore, the gloves protect the player's skin from potentially hazardous laser radiation and give audiences a more visual impression of the instrument being played.

In 2008 Maurizio Carelli, an Italian software and electronic engineer, has invented a new portable two-colors laser harp, named "KromaLASER KL-250" with only 80-100mW Laser Beams, for the company: Kromalaser. This was a prototype. After that experience he developed the definitive and powerful version of laser harp named "KromaLASER KL-450". The device features a configurable full octave with green beams for any diatonic note and red ones for any chromatic note for full Diatonic and Chromatic scale. In the second half of 2010, he has also invented a full color version of the device, fully "plug & play" and Daily Light independent, standalone models (with 1W Laser) named KromaLASER KL-PRO or capable to drive ILDA laserscanners using also Blue Color realizing the first multi-color laser harp controller: KL-Kontrol which prototype's name was: KL-ILDA (Copyrighted in July 2010)

In Februari 2010 the laser harps of M.Carelli, where shown in the WIR-IN-MILAN show

In September 2010 during Sound and Multimedia Fair in Zagreb Croatian company Prolight made world premiere of ILDA Laser Harp Controller. It was award winning performance, and Prolight Laser Harp Controller gain huge success.

In January 2011 world's first full color laser harp controller for ILDA compatible laser projectors was commercially introduced named Prolight Laser Harp Controller LH1 and next month new Laser Harp dedicated web page was made. Prolight Laser Harp Controller LH1 is fully plug&play, daily light independent, polyphonic Laser Harp Controller which can work with any type of ILDA compliant laser projector, turning it into laser harp.

Users can switch between several modes with different number of beams as well as several beam color combinations including full color rainbow mode, bi-color, and single color combinations. Prolight Laser Harp Controller’s design does not include a built-in laser projector, which enables the users to freely choose their own laser setup for every performance, whether they need a less powerful laser projector for indoor events or a high-powered laser for open air performances. It can be used with monochrome lasers or full color lasers as well.

Unframed style, "Image recognition" laser harp

The image recognition laser harp is also an unframed design, but uses a high-speed USB camera connected to a laptop computer, instead of a photodiode to detect the reflected light from the hand breaking the beam. The digital picture is analyzed by the computer software to determine which beam is broken and send the appropriate MIDI signal back to the synthesizer, which is responsible for creating the sound. The computer also controls the laser projector via an ILDA USB laser controller.

Framed style

The framed style, which is often created to look like a harp with strings, uses an array of photodiodes or photoresistors inside the upper or lower part of the frame to detect blocking of the laser beams.The lasers can be mounted on the 'neck' or upper side of the harp, shining down, or on the body, shining up. Typically, the lasers used are very low-powered 5 mW red or green lasers, which are considered safe for public interaction by the FDA. Any number of laser beams can be arranged in this type of laser harp, from as few as one or two, up to 32 or more, depending on the capacity of the MIDI controller(s) and software being used. This style of Laser Harp can be created in any size, from a lap sized harp to a room sized installation, or larger, like the installations seen at Burning Man. In this design, only an analog DC (on/off) trigger is created by the breaking of the beam (and the DC circuit made by the beam shining on the optic sensor), which is sufficient to trigger any number of events (musical or otherwise) as determined by the data analyzer/software in question. In the MIDI controller, this analog DC current interruption is converted to a digital signal, which is then used to trigger many possible events or actions. Some software comes equipped with full wave file editors and synthesizers, and can also trigger video and still imagery via projection units.

Typical framed style laser harp software functions

Play Modes:

• Trigger Mode — In this mode, breaking a beam always triggers the event, sound (a sample, loop or MIDI note), image or video that that particular beam has been preset to trigger. Each beam will always trigger its own preset event when broken. e.g. If the beam number one is set to play a bass drum and beam two a snare drum; then one will always play a bass drum and two a snare.

• Sequence Mode — In this mode, breaking any of the beams plays a preset melody or song one note at a time. Familiar tunes may be played by the breaking the beams in time with the song. Little or no musical ability is required to play a tune. Similarly, a sequence of images could be displayed or an image could be built up one part at a time.

• Event Mode — When broken, a beam set to 'Event Mode' can change octaves, sounds, songs or programmed settings for any or all of the beams.

Switch Modes:

• On-Off — A sound will play only while a beam remains broken. The sound stops when the beam is unbroken.

• Play to end — Once triggered, a sound will play to the end regardless of when the beam is unbroken.

• Toggle Mode — Breaking a beam the first time triggers a sound which plays to the end (or loops) until the beam is broken a second time.

All beams do not have to be set to the same Play or Switch Mode - each beam may be set up differently.

Safety considerations

In order to produce laser beams visible in normal air, a relatively powerful laser is needed; at least about 20 mW of power, depending on the type of laser and the design of the instrument, is required in order to produce a visible array of beams. However, a considerably more powerful laser is needed to yield spectacular results, generally 500 mW or more. In any case, class IIIb or IV lasers will usually be necessary, introducing a significant risk of skin and eye damage unless precautions (gloves and protective glasses) are taken.

Use in Jean-Michel Jarre concerts

The laser harp is one of the most famous instruments used by Jean Michel Jarre in his concerts. The original laser harp was made by Geoffrey Rose in 1975/6 and he coined the name laser harp at that time. Bernard Szajner made a version in 1981 for The Concerts In China tour for a track simply titled Laser Harp (or Harpe Laser in it's original French), the instrument is used in almost every concert with the exception of Aero. It is almost always used in the second part of Second Rendez-Vous, but has also been used for tracks including Third Rendez-Vous, Chronologie 3, Calypso 2, and Oxygene 7. The characteristic sound of the laser harp in Jarre's performances is generated by a factory preset on the Elka Synthex synthesizer.

Some people suspect the laser harp, as well as some other custom instruments, is a fake; careful inspection of concert footage of Jarre playing the harp occasionally indicates that striking the same beam produces different notes, suggesting that the harp is simply designed to trigger the next correct note irrespective of which beam is broken. However, this method is unreliable, as videos are invariably edited before release. As an example, in the live recording of the Paris La Défense concert as broadcast on the Europe 2 radio station, it can be clearly heard that the laser harp is malfunctioning, and in fact after a while gets replaced by a different synthesizer. In the video release, no trace is left of this malfunction. Also the harp is fitted with foot pedals for selecting scales, making it quite plausible that the same beam can house different notes.

During Jarre's 2009 In-doors Arena Tour, he commented on his blog that he "should make a few intentional mistakes for people to really understand that it is live". Later the same day, at a concert in Helsinki, the harp "suddenly froze in Rendez Vous 2 for unknown reasons".

Recently, Steve Hobley was able to reproduce a working model of Jarre's harp using a 250 mW green laser, scanner and some inexpensive components (including a Wii Remote). Plans and source code were formerly to be found here (as of Sept 12th 2010 plans are no longer sold through his website). Other amateur harp builders have subsequently followed in his path.