Godfried-Willem Raes

"Virtual Jewsharp Project"


Audio-Art Installation

This project, an audio-art installation as well as a concert instrument, evolved from the composers more than 20 years of research in the area of non-positional body movement to sound conversion technology. The project makes use of electromagnetic radar technology for the detection of acceleration, velocity and moving body mass. The system operates in the 10 to 20 GHz frequency band. Audio transformation equipment is used in the process of rendering an acoustically interesting effect. In contrast to the composers large scale compositions 'A Book of Moves(1992)' and 'Songbook' (1995), where the technology used for the implementation of the invisible instruments is largely digital, these "Virtual Jewsharps" are mostly analogue instruments.

The project is an implementation of a virtual jewsharp, since the movements needed to truly play it closely resemble those required to play the acoustic jewsharp. Of course, since no real and physical object is involved, the cavity resonance of the mouth is not used here as a means for timbral and harmonic control of the instrument. Instead, acceleration is used for the melodic aspect of the sounds and body mass for the global sound volume.

Other than in the case of Godfried-Willem Raes' 'Holosound' system, this instrument is very sensitive to angular and vectorial aspects of the performed movements, as well as to absolute distance from the radar devices used.

This project was premiered in the Austrian town Krems at the occasion of the 'Zur.Zeit - Klangprojekt' from 14.07.1993 to 18.07.1993. At Krems the invisible instruments were set up in the mediaeval gates through which the town can be accessed. These gates are rather long and rectangular, almost entailing longitudinal movements. Thus, whoever wanted to get in or out of town, got to play the instruments.

In 1995 the project was installed in the caves (mergelgrotten) near Maastricht, Netherlands. Later, it was demonstrated at many science and art&science fairs in technical highschools and universities all over Europe. In 1997, is was hosted in the 'Oorsmeer' festival at Vooruit in Ghent.

Concert piece

The concert piece, makes use of the same instruments that are used in the audio-art installations as described above. However, here four separate radar instruments are played by four different soloists on stage. The piece became the authors first attempt to write and realize a piece using invisible instruments to be played by more than one single player at once, as was the case with the authors 'invisible instruments'. Due to the nature of the radar technology used, it became now possible to tune the four radar devices needed, to individually different frequencies and so different players can play in a same space independently of each other. Such was proven to be impossible with the sonar based technology the author developed for 'Holosound' and 'A Book of Moves' and 'Songbook'.

The piece was premiered by Zachar Laskevicz, Xavier Verhelst and the author at Logos Foundation , Tetrahedronhall, on august 11th and 12th, 1993.

Technical limitations - notes for organizers...

This technology can only be used at locations free of ionising sources. So places with permanent electroluminiscent tubes of any kind (including sodium vapour), CRT's, X-ray equipment, particle accelerators, satelite communication and TV emitters/repeaters are not to be considered for performances nor installations of these devices. This condition must be fullfilled by the organizer wanting us to set up and operate this project.

The devices need an absolutely clean DC power supply of 12 Volts. Since the ideal power source meeting the specifications is the classical lead battery as found in almost every normal car, we require the organizer to provide us with a charged 12 V car battery for each radar device to be installed. Lead batteries are not allowable air-transport luggage, which is, apart from the weight involved, why we will not carry them with us on concert tours. A capacity of 7 Ah is enough for more than 24 h uninterupted operation of one of these devices, so a good car battery should last for well over a week.

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Published on the web on July 29th 1997 by Godfried-Willem Raes

Last updated: 2016-10-17