Atli organised two major events in Reykjavík in the 1970s: the Festival of the International Society for Contemporary Music in 1973 and Nordic Music Days three years later. These events were a turning point in Icelandic musical life, creating new links with many other countries. In 1980, Atli established the Myrka músíkdaga Festival of Music (Dark Music Days), which is held on the shortest day of the year and provides a platform for Icelandic composers both young and old.
Atli became the first Icelander to win the Nordic Council’s award for composition for his flute concerto written in 1976. He was elected to the Royal Swedish Academy of Music in 1993. He has lectured in many universities in Scandinavia, Germany and the USA. In 2002-03 he was Visiting Professor at Brown University in Providence, Rhode Island. He was appointed Composer in Residence for the Icelandic Symphony Orchestra in 2004.
Atli has written a wide range of works, including four symphonies, nine concertos, five operas and a large number of chamber pieces. His works have been performed all around the world. Atli has also written music for the theatre and composed many songs that have been become part of Icelandic musical culture.