Ástmar studied piano and singing in Iceland and, after graduation, enrolled at the Royal Academy of Music, London, where he studied piano with Philip Jenkins and singing with Henry Cummings. He continued his studies privately in London with Louis Kentner on piano and singing with Kenneth Woollam. Astmar worked as Head of Keyboard at Bradfield College, Berkshire before moving up to Scotland. As a pianist he has performed widely and recorded for the Icelandic Broadcasting Corporation. He has also sung all over the UK, Iceland and Germany in opera, oratorio and recitals.