Since the 1960s, when he met Cornelius Cardew and helped found the Scratch Orchestra, Parsons has been strongly associated with the English school of experimental music.
In 1969 Cardew, Parsons and fellow composer Howard Skempton founded the Scratch Orchestra, an experimental free ensemble devoted to performing contemporary music.
Parsons was among the Orchestra members who refused to be associated with the Maoist politics Cardew was propagating, and left.
Since the early 1960s Parsons has also been active as a writer on music; his writings include a number of important articles on contemporary English composers.
Parsons' music is influenced by Anton Webern, composers of the so-called New York school (John Cage, Morton Feldman and Christian Wolff), various English composers he met through Cardew and the Scratch Orchestra, and, since the Portsmouth years, "Systems" artists such as Malcolm Hughes and Jeffrey Steele.