Born in Talysarn, in the Nantlle Valley, he was educated at Talysarn Primary School and Ysgol Dyffryn Nantlle, Penygroes. He has a degree in Music from Cardiff University and a Diploma in Librarianship from Aberystwyth. A member of the successful and well known choir, Côr Rhuthun a’r Cylch since 1981, and an accompanist and composer for the choir since 1987, he was appointed conductor of the choir in 2007. Now retired, Arwyn is busy composing and adjudicating at various Eisteddfodau. He also presents a programme of music on Radio Cymru on Sunday morning. He is married to Mari, and have two children.
He wrote Memory of Stars (Atgof o’r Sêr) for the National Eisteddfod in 2001, and Benedictus (from Er Hwylio’r Haul) for the National Eisteddfod 2005 which was recorded originally by Bryn Terfel and Rhys Meirion and was later included by The Priests on their classical album in 2008. This reached No. 1 in Ireland and Norway, Belgium and Sweden as well as holding the No. 1 position in the USA for 23 weeks.