Lyon was born in Halifax, in England's West Yorkshire region, growing up in nearby Illingworth and singing in the choir at Halifax Parish Church. He attended Harrow School in London, appearing as an actor in school productions, and he later observed that opera was for him a compromise between his dual desires to act and sing. Until he was 18, Lyon had an alto voice, but he then switched to tenor. He went on to St. John's College, Cambridge, as a choral scholar. At St. John's, he majored in (read) art history but continued to sing, and after graduating, he enrolled at the Royal Academy of Music and the National Opera Studio for further vocal training. His first big break came when he was cast by pioneer Baroque opera conductor William Christie in a production of Handel's opera Hercules, HWV 60, at London's Barbican Centre. Since then, his roles have focused predominantly, but not exclusively, on the Baroque era; his repertory extends through Britten and Stravinsky and as far forward as the late 20th century. He has appeared at most of Britain's top opera houses and several prominent houses abroad, including the Bavarian State Opera, the Teatro Real in Madrid, and La Monnaie in Brussels. Frequently appearing in concert performances, Lyon has the tenor parts in Handel's Messiah, HWV 56, and Elgar's The Dream of Gerontius, Op. 38, in his repertory. A notable feature of Lyon's public persona is that his status as an openly gay artist is emphasized. Lyon made his recording debut in 2012 with the London Baroque on an album of Handel works. In 2019, he appeared with the chamber group Theatre of the Ayre on 17th Century Playlist, a collection of opera and song. ~ James Manheim, Rovi