Pendulum Music (For Microphones, Amplifiers Speakers and Performers) is the name of a work by Steve Reich, involving suspended microphones and speakers, creating phasing feedback tones. The piece was composed in August 1968 and revised in May 1973, and is an example of process music.
Three or more microphones are suspended above the speakers by means of a cable and stand. The microphones are pulled back, switched on, and released over the speaker, and gravity causes them to swing back and forth as pendula. As the microphone nears the speaker, a feedback tone is created. Different lengths of cable will swing at different speeds, creating an overlapping series of feedback squeals. The music created is thus the result of the process of the swinging microphones.
According to Reich, "The piece is ended sometime shortly after all mikes have come to rest and are feeding back a continuous tone by performers pulling the power cords of the amplifiers".
In 2012, Richard D James performed a version of the piece using lasers reflected off of giant Newton's cradles.
References
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