Composition on source recordings from Skarnsundet bridge. To me it looks like a big harp! I was very happy to be asked to make a piece with it. The beautiful architecture of the stayed cable bridge informs formal aspects of the composition, and the dispersive quality of the cables is a main timbral theme. Special microphones based on accelerometers were used to capture the ultra-low frequencies of the cables. The cables has a length of up to 280 meters and a fundamental frequency as low as 0.5 Hertz for transverse waves. Due to the physics of these cables-as-strings the longitudinal waves has a significant contribution to the sound. The longitudinal waves exhibit strong dispersive qualities, so high frequencies travel faster than low frequencies. This give rise to the pitch sweep that can be heard when hammering the cables with the palm of the hand. To enable the musical use of the low fundamental frequencies, various techniques of transposition and spectral manipulation was implemented. Spectral pitch modification allows transposition without altering the temporal structure of the sound. The slow changing amplitude of the transversal waves (below 1 Hz) are also used as a control signal to modulate the amplitude of granular noise textures, allowing the movement of the cables to be heard as musical sound. Looking at the architectural shape of the bridge and cables from the side, one can see the large arcs held up by the two bridge towers. This shape was used as pitch trajectory maps to further embed the nature of the bridge in the sonic result. The bridge also has a metal railing of several hundred meters length. This exhibit bell-like characteristics and is easily exited by both wind and passing traffic.

The composition is part of a pilot project for a larger permanent sound and light installation that I was working on in collaboration with visual artist Viel Bjerkeset Andersen. The larger installation was not realized, due to funding issues (budgeted to a total of 6M NOK…). The art project on the bridge was initiated by the municipalities of Inderøy and Mosvik, merging into one municipality on January 1st 2012.

Overview
Skarnsundet Bru as seen from the Mosvik side

The composition an be heard on Soundcloud, and also in the video below.

The video artist Pekka Stokke made this video to complement the composition

While working on recording source material from the bridge structure, I had mounted microphones and other devices along railings and staycables, getting power from a few hundred meters of extension cable… While I was working, the police came by, wondering wwhat I was up to. I soon realized that people in passing cars had become concerned about a potential terrorist action and had queued up, not wanting to drive across the bridge. After some explanation on my part that this was a rather innocent art project, traffic was allowed to continue.

Composer at the bridge
Recording sounds from the bridge

Tags: soundart, music

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