Lewis was born in Neath, where he joined the church choir and began learning the organ, and now lives in Llanfairfechan.
[1] He studied at the University of Wales, Cardiff, under Alun Hoddinott; with György Ligeti and Karlheinz Stockhausen at Darmstadt; with Bogusław Schaeffer in Kraków and with Don Banks in London.
Early performances included Fanfares with Variations and the Chamber Concerto with the BBC Welsh Orchestra under John Carewe, and, at the 1967 Cheltenham Festival, his Two Cadenzas for piano and Epitaphium - Children of the Sun for narrator, chamber choir, piano, flute, clarinet and percussion.
BBC commissions[1] included the orchestral works Mutations I (1969), Aurora (1973), Scenario (1975), Praeludium (1975), Memoria (1978) and Limina Lucis (1982).
[2] In 2005 Ivan March in Gramophone magazine described the CD release of Epitaph for Abelard and Heloise, Litania and Musica Aeterna as "...a disc not to be missed by anyone who cares about communicative 20th-century music."