A contemporary German-Dutch composer. He studied church music in Braunschweig, composition, piano, analysis and acoustics in Detmold, music representation techniques in Cologne and computer technique in Bonn. He attended and later lectured at the Darmstadt music summer schools. From 1954 to 1964 Koenig worked in the electronic studio of West German Radio (WDR) producing his electronic compositions Klangfiguren, Essay and Terminus 1 and wrote orchestral and chamber music. Furthermore he assisted other composers, including Kagel, Evangelisti, Ligeti, Brun and Stockhausen (with the realization of Kontakte and Gesang der Junglinge).
In 1964 Koenig moved to the Netherlands, where he was, until 1986, director and later chairman of the Institute of Sonology at the University of Utrecht. Here he developed his computer composition programs Project 1 (1964) and Project 2 (1966), designed to formalise the composition of musical structure-variants. Both programs had a significant impact on the further development of algorithmic composition systems.
His sound synthesis program SSP (started 1971) is based on the representation of sound as a sequence of amplitudes in time. It makes use of the methods of aleatoric and groupwise selection of elements employed in Project 1 and Project 2. He continued to produce electronic works (Terminus 2, the Funktionen series). These were followed by the application of his computer programs, resulting in chamber music (Uebung for piano, the Segmente series, 3 ASKO Pieces, String Quartet 1987, String Trio) and works for orchestra (Beitrag, Concerti e Corali). Five volumes of his theoretical writings were published between 1991 and 2002 under the title Aesthetische Praxis by Pfau Verlag; an Italian selection appeared under the title Genesi e forma (Semar, Rome 1995).