Born in Bærum, Norway, Hellstenius studied musicology at the University of Oslo and composition with Lasse Thoresen, Olav Anton Thommessen and Bjørn Kruse at the Norwegian Academy of Music in Oslo. He studied in 1992–1993 with Gérard Grisey at the Conservatoire National Supérieur de Musique et de Danse de Paris in Paris, and he also studied computer-supported composition at IRCAM.

Hellstenius is currently professor in composition and music theory at the Norwegian Academy of Music.

Hellstenius’ compositional output spans a wide stylistic field, including opera, chamber music, orchestral works, electro-acoustic music and scores for theatre, film and ballet. His works have seen performances throughout the Nordics, Russia, Australia, the U.S., Canada, England, Scotland, Greece, Estonia, Lithuania, Latvia, Poland, Germany, France, Holland and Japan. His works have been featured at festivals such as the Bourges Festival for electro-acoustic music in France, the International Rostrum for Composers in Paris, the DUT-festival in Copenhagen, Nordic Music Days and the ULTIMA Oslo Contemporary Music Festival, performed by ensembles Cikada, Oslo Sinfonietta, BIT20 Ensemble and Ensemble Court Circuit.

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