Denley was born in Bulli, a small country town in the state of New South Wales, Australia, and grew up in nearby Wollongong. His father, an amateur violinist and music enthusiast, gave him his first violin at the tender age of five. In 1969, the young Denley entered the NSW Conservatorium to study flute with Peter Richardson, who turned him to contemporary composers like Varèse and Berio. His influence and the child's growing interest in left-field jazz determined his unusual direction, but it would be a few years before he took music seriously. Around 1977, he decided to become a professional musician and started to search for his own style. He met percussionist and instrument-builder Peter Ready in Robert Lloyd's ensemble. In 1979, they built a set of large junk-metal instruments and toured Australia with these New Music Constructions for two years, releasing an LP along the way (25th April 1980, on Wombarra).
The meeting with Jon Rose took place in 1981. Both had similar backgrounds as classically trained musicians playing jazz and studio gigs to pay the rent while searching for a higher form of expression. The variable-geometry group the Relative Band, active from 1981 to 1985, became a laboratory and a talent pool for the then-burgeoning Australian free improv scene. The group also attracted foreign musicians, especially from London. Another long-lasting collaboration started in 1983 with Rik Rue (a Relative Band alumni). They formed Mind/Body/Split and later joined Machine for Making Sense. Meanwhile Denley began to visit London regularly, eventually splitting his time almost evenly between Europe and Australia. In 1986, he formed Embers with Chris Burn, Marcio Mattos, and John Butcher. He made his the esthetics of these musicians inspired by the Spontaneous Music Ensemble.
Since then, Denley has multiplied collaborations in Europe and Australia. During the 1990s, he toured and recorded with Chris Burn's ensemble, Machine for Making Sense, and Lines (formed in 1996, with Axel Dörner, Marcio Mattos, Philipp Wachsmann, and Martin Blume). His first solo album, Dark Matter, came out in 1995. In 2002, he released a duo CD, Tibooburra, with his wife. ~ François Couture, Rovi