Critical Acclaim(Cello Concerto) ...exquisitely-textured structure ... [it] is a work of haunting beauty. Instantly characterised by its slow, soft, deep pulsing tread, the concerto...generates an unfailingly evocative sound world...The music is superbly sustained in its overall mood... a delicately-orchestrated cloud of soft, magical sound, is amazing, ethereal and mesmeric. - Michael Tumelty, The Herald
Hallgrímsson's music is characterized by rhythm and by a differentiated play with tone colors... done with outstanding craftsmanship. - Lübecker Nachrichten
Despite his success as a performer, the urge to compose became stronger and in 1983 Hallgrímsson left his post with the Scottish Chamber Orchestra to devote himself to this activity full-time. His catalogue includes instrumental, chamber and orchestral works and he achieved international recognition for the highly successful Poemi for solo violin and string orchestra, which was awarded the prestigious Nordic Council Prize in 1986 after winning second prize at the 1985 International Wieniawski Competition and the Icelandic Dagbladid Visir Cultural Prize.
Poemi turned out to be the first in a series of works for solo instrument and string orchestra; it was followed by Ríma (1993) for soprano and string orchestra, commissioned by the Olympics committee for the opening of the 1994 Winter Olympics and premiered by the Norwegian Chamber Orchestra, and Herma (1994-5), a concerto for cello and string orchestra for William Conway and the Scottish Chamber Orchestra. The last in the series was the viola concerto Ombra (1999), which was commissioned by the Icelandic Broadcasting Corporation and premiered in Scotland by Lars Anders Tomter and the Scottish Chamber Orchestra under Mikko Franck in October 1999.
Although he admits to some major influences, Hallgrímsson’s musical style is entirely original, showing a sensitivity to line and colour, shape and texture, not surprising from a composer who in 1969 performed one of his earliest compositions, Solitaire for solo cello, surrounded by an exhibition of his own drawings and paintings. Such involvement with the visual arts remains a key influence on Hallgrimsson’s musical style and in 1996 he was commissioned by the Scottish Chamber Orchestra to write Still Life, in conjunction with a specially commissioned painting by Craigie Aitchison. Aitchison's work is also an influence behind Hallgrimsson’s Symphony No.1 (Crucifixion) (1997), commissioned by the Royal Philharmonic Orchestra as part of the Maxwell Davies Millennium Programme of commissions.
Also at this time, a commission from the Northlands Festival in Scotland demonstrated Hallgrímsson’s growing interest in music theatre. Mini-Stories (1997) for narrator and ensemble set translated texts by the Russian absurdist Daniil Kharms. Its deft evocation of a unique world of humour, nonsense and melancholy has been widely acclaimed by audiences and critics, and since its premiere the piece has been taken up by several ensembles. In 2003 Hallgrímsson turned to Kharms’s texts once more in the absurdist opera Die Wält der Zwischenfälle, co-commissioned by the Lubeck Theatre and NetzZeit in Vienna. The opera was acclaimed as a great success in Germany and also in Iceland, where it received a concert performance in 2007.
Also in 2003, Hallgrímsson finally produced a long-awaited Cello Concerto, commissioned jointly by the Oslo Philharmonic, the Iceland Symphony Orchestra and the Scottish Chamber Orchestra for cellist Truls Mørk, who has since championed the work in a number of performances across Europe. Two years later, he produced his largest chamber work to date, Notes from a Diary (2005) for viola and piano, an intensely moving evocation of the feeling of standing outside Anne Frank’s former house in Amsterdam.
Recent years have seen an ever-increasing amount of interest in Hallgrímsson’s music, with a number of significant performances, and the release of a number of portrait CDs featuring his choral music, orchestral music, chamber works and keyboard music. In 2008 the Iceland Symphony Orchestra announced Hallgrímsson as their composer in residence – a three-year association that will encompass performances, new commissions, and a premiere recording of his 1st Symphony.