Laser harp

Jarre playing the 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 in his concerts.

The term "laser harp" and the first working laser harp were invented and made by Bernard Szajner in 1981. 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); 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. 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.

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 lasers 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.jared paaske rocks

Use in Jean-Michel Jarre concerts

The laser harp is one of the most famous instruments used by Jean Michel Jarre in his concerts. First created by Bernard Szajner for The Concerts In China tour, the laser harp is used in almost every concert for playing the second part of Second Rendez-Vous and in other songs as well (it usually appears two or three times in a concert).

The laser harp was not used on his Aero concert but it was revived in 2004 and has been used since then, mostly on his tracks Second Rendez-Vous and Third Rendez-Vous.

Although the laser harp makes no actual sound itself, (merely triggering a note on a synthesizer) Jarre has consistently used it to trigger a particular sound which has become synonymous with his use of the laser harp, which is based on a preset from 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.

Others believe that the laser harp has been proven to work and has been played by Jarre live occasionally, especially on his 1997 concert tour and Oxygen in Moscow. Other notable live playings of the harp occurred during Chronologie 3 at Beijing as well as at Hymn to the Akropolis and during Calypso 2 at Paris La Defense. In the European Tour 1997 Jarre played Laser Harp for the first song on that concert, the famous first notes of Oxygene VII, played three times without any other instrument or sound. Also, there was a laser harp on display at the 1989 Concert d'Images exhibition in Paris, which could be played by the public.

However, the harp at the Manchester venue of the Europe in Concert tour was certainly only for visual purposes as the laser failed during the performance but the lead line, actually played on stage by Francis Rimbert, continued. This may have depended on the viewpoint as from another viewpoint, with a clear view of the harp, Jarre, and Rimbert, the harp functioned perfectly throughout.

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 250mw green laser, scanner and some inexpensive components (including a Wii Remote). Plans and source code can be found at here

See also

• Laser safety
• Laser lighting display
• Beamz

External links

• Custom one-of-a-kind Laser harps created by Mountain Glen Harps
• The Laser Harp Pages
• Laser Harp of Laser Spectacles
• Guide to creating your own laser harp
• Recent laser harp projects by Blueink Studios
• Steve Hobley's Arduino powered laser harp project
• Anno Domini's laser harp