Reynolds joined A Flock of Seagulls (at the age of seventeen) a few months after the band was formed to replace original guitarist Willie Woo. The group's popularity soared in the early 1980s with the release of "(It's Not Me) Talking," and in 1982 the song "I Ran (So Far Away)" was a hit in the US and at home. By the time he was twenty-one, the band had released an album, won a Grammy Award, got two more hit singles, and did a worldwide tour. Reynolds, whose "textural wash" was influenced by U2, contributed significantly to the group's sound and was praised for his "echo-laden" "unique guitar style", which differentiated Flock of Seagulls from other synth-heavy bands of the period.
Reynolds left the band in 1984, after the release of The Story of a Young Heart, two years before the band broke up. When it was reformed in 1989 by singer Mike Score, Reynolds and the remaining members decided not to rejoin. Reynolds and his fellow ex-members did, however, reunite with Score for a one-off performance in London in 2003 for VH1's Bands Reunited television program. The band performed their hits "I Ran" and "Space Age Love Song" in front of a staged audience arranged by the program's production team. Before the performance, Reynolds was interviewed about why he left the band; he claimed that he was too young for the "rock 'n' roll lifestyle" and that he was exhausted from all of the performances. Since leaving Flock of Seagulls, Reynolds has been playing guitar with jazz bands in England.