Reactor was composed or the reed trio Ritual Action, comprised of oboist Andrew Nogal
, clarinetist Andy Hudson
, and bassoonist Ben Roidl-Ward
. It is in three main sections, each separated by a bassoon solo. The first section introduces the main motives — a slow melody in the oboe, a pair of figures played by the clarinet and bassoon in parallel, and a strident rising motive in the clarinet. The second section develops those themes and motives at a more agitated pace. During the second bassoon solo, the other players switch to lower versions of their instruments, leading to the heavy groove that begins the third section, building intensity to the rapid, driving conclusion.