Justin Connolly was born in London on 11 Aug 1933, and was educated at Westminster School. He was at the Middle Temple before entering the Royal College of Music in 1958, where he studied composition (with Fricker) and conducting, winning prizes for both activities; simultaneously he had frequent informal contact with Gerhard. The music he wrote during this period was fluently composed in a Schoenbergian 12-note serial style, but was all subsequently withdrawn. In 1963 he went to Yale University on a three-year Harkness Fellowship, as a student of Mel Powell and later as a teacher, during which he found his individual voice and consolidated his outstanding technical mastery.

His earliest acknowledged works proceed largely by the scintillating play of small motifs within complex textures. They employ space-time notation and grace-notes as well as traditional metre in a virtuosic mixture. The series of Triads exemplify this, and also provide an example of his penchant for groupings of highly diverse instruments, which is carried through into the concertante textures of his works for larger forces. By the time of Anima and Diaphony (both commissioned for the Proms) Connolly had expanded his expressive range to encompass an increased directness and simplicity as well as the fragmentary motivic working typical of earlier works.

Ill health led to a period from 1978 to 1988 during which he produced only revisions of earlier works. His next new work, Spelt from Sybil's Leaves, came in 1989 in response to a BBC commission, and is for a typically unusual scoring. The vocal lines display sensitive and expressive word-setting (a characteristic of all his vocal music), but also a more sustained melodic impetus hinted at in his work of the late 1970s. During the 1990s, Connolly completed a steady stream of works, both substantial and occasional, culminating in Scardanelli Dreams, a formally and rhythmically complex work in which five fragments of Hölderlin are sung in parallel with ten solo piano movements of various sizes. The resulting work has unusual poetic power, providing ample proof of Connolly’s sustained ability to steer a course between technical brilliance and expressive import.

He was an experienced and respected broadcaster and teacher (RCM 1966-1988, RAM 1989-1996) In 1982 he was visiting lecturer in composition at the University of Melbourne, and in 1979-80 visiting lecturer in composition at UC Santa Barbara.