Born in London, William Attwood received composition lessons from Michael Finnissy at Oxford University. Later he was a pupil of Simon Bainbridge at the Guildhall School of Music and Drama, and of Theo Brandmüller at the Hochschule für Musik Saar.
His first commission was for Tourbillons, premiered in 2000 by the London Sinfonietta under Pierre-André Valade at State of the Nation and described in The Independent as "glittering but severe". 2005 saw the completion of Iwwer Tiermen, in which The Guardian commented on "mysterious rustlings and throbbings, and empty stillness juxtaposed with moments of maximal activity". The work appeared in the Jerwood series of CDs in 2008. The London Sinfonietta also gave the UK premieres of En este sitio... , first performed in Brussels by Ictus, and Porthleven, written for Nouvel Ensemble Moderne of Montreal.
William has also worked with the City of London Sinfonia, who premiered Colour down the side and Black and White Verticals, as well as with numerous first-class ensembles including Reconsil of Vienna, Signos of Mexico City and Duo Konflikt of Karlsruhe.
William currently spends much of his time in the Saar region of Germany working with the conductor Jonathan Kaell as co-ordinator of Grenzpunkt, the new music ensemble of the Hochschule für Musik Saar. His works have been widely peformed in the Saarland: Vivid Screening appeared on CD in 2005 with support from the Saarbrücken-based Forum Junge Talente, and Brinquebalant was performed in 2007 at the annual festival Musik im 21. Jahrhundert, and broadcast by the Saarländischer Rundfunk. Embrouillement was recorded for the radio series Musik an der Saar. En Frente was commissioned by Netzwerk Musik Saar for the Luxembourg Sinfonietta and performed across the region to celebrate Luxembourg as European Capital of Culture in 2007. Rotes Gewölk, commissioned by the Saarländischer Rundfunk in 2008, was performed that year at the International Summer Courses for New Music in Darmstadt.
Outside the Saarland, William is composer in residence to the St. Paul's Sinfonia in London, for whom he is writing a double bass concerto. His plans also include a piccolo concerto for Ensemble Reconsil, and a chamber work for the Chilean group Taller de Musica Contemporanea.
