Icelandic composer Atli Heimir Sveinsson was born in Reykjavik on 21 September 1938 into a musical family, and was sent to Heinz Edelstein's Youth Music School from the age of nine. He studied at the Reykjavik College of Music and later at Staatliche Hochschule für Musik in Cologne, where his teachers included Bernd Alois Zimmermann. Whilst in Germany he attended summer courses in Darmstadt, meeting Messiaen, Boulez, Ligeti and Bruno Maderna. In 1964 he studied with Karlheinz Stockhausen, and the following year he studied electronic music in the Netherlands with Gottfried Michael Koenig.
From then on, he lived in Iceland, founding the composition class at Reykjavik College of Music and working as a freelance producer at the Icelandic State Broadcasting Service. From 1972 until 1983 he was president of the Icelandic Composers Association. He organised the Festival and General Assembly of the International Society for Contemporary Music in Iceland in 1973. He was president of the Nordic Composers Council (1974-6) and organised the Nordic Music Days in Reykjavik in 1976 - events which became a turning point in Icelandic musical life, bringing it closer to Scandinavia, Europe and the USA.
He founded Dark Music Days, a festival for contemporary Icelandic Music, in 1980. Initially held biennially, it later became and annual forum for the presentation of new Icelandic music.
He became the first Icelander to receive the Nordic Council Music Prize, in 1976, for his Flute Concerto.
The Icelandic Parliament granted him a lifetime honorary salary in 1992, and in 1993 he became a member of the Royal Swedish Academy of Music.
His output included six symphonies, the second of which was first performed in Reykjavik on 1 June 2006, nine concertos and various orchestral, chamber and solo works. He also wrote the operas The Damask Drum (1980), Vikivaki (1982), Iceland: My father's country, The moonlight island, Hertervig and The Conversion. Time and Water is a ballet-oratorio on a poem by Steinn Steinarr. Much of his output has become part of Icelandic musical culture.
Sveinsson's death was announced on 21 April 2019, aged eighty.