[1] He was a member of Aosdána, an elite association of Irish artists.
He studied in Ireland, England, Belgium and Italy, including at the Conservatorio Santa Cecilia.
[3][4] Sweeney composed in a minimalist style influenced by Béla Bartók, Olivier Messiaen, Andrzej Panufnik, John Adams and Steve Reich.
Over his career, he composed two symphonies, five concertos, three operas and choral works, including the cantata Deirdre.
He was Head of the Music Department at Waterford Institute of Technology until 2010.