He founded the Guildhall New Music Ensemble and also conducted the London Jazz Composers’ Orchestra between 1970 and 1980, the latter stimulating his particular interest in improvisation.
[3] His pupils included Deirdre Gribbin, Barry Guy, Gary Higginson, Philip Sawyers and Debbie Wiseman.
[2][4] In 1990 Orr gave up regular teaching to devote more time to composition, and lived with his second wife Jean Latimer in the Wye Valley until his death.
[6] His style is notable for its interest in structures that evolve through continuous variation, often with his personal take on 12-tone serialism, using tonal intervals and octave doubling.
[11] During the 1980s Orr composed three music theatre pieces: Unicorn (1981), The Last Circus (1984) and Ring in the New (1986), and a number of song cycles, including the "caustic" Ten Types of Hospital Visitor (1986), setting Charles Causley.