Agnar Már Magnússon began musical studies at a young age. After graduating from the FÍH school of music in Reykjavík and Conservatorium van Amsterdam in the Netherlands, he studied with Larry Goldings and other private instructors in New York. There, he also was introduced to many known jazz musicians and that led to the recording of his first CD titled "01". "O one" was released in and distributed around the world by the Spanish record company Fresh Sound-New Talent. Since then, Agnar has released many CDs, most of which have been nominated for the Icelandic Music Awards. These include "Tónn í tómið", a live recording of a piano duet with Ástvaldur Traustason, and two CDs with the B3 trio, Fals and Kör, where Agnar plays a Hammond organ. 

Agnar also released original music to the play 1900, which was staged in the Icelandic National Theatre in 2005. Agnar has arranged music for CDs and musicals, worked with The Reykjavik Big Band for many years, played in concerts in Iceland and abroad and been musical director in the theatre. He has played/recorded with among others Bill Stewart, Seamus Blake, Ben Street, Ingrid Jensen, John Hollenbeck and Drew Gress.