Ionisation (1929–1931) is a musical composition by Edgard Varèse written for thirteen percussionists. It was among the first concert hall compositions for percussion ensemble alone, although Alexander Tcherepnin had composed an entire movement for percussion alone in his Symphony No. 1 from 1927. In the journal Tempo, percussionist Brian Holder writes, "The work presented the important notion that unpitched percussion could stand alone as a serious form of concert music – a relatively unexplored concept at the time."

Edgard Victor Achille Charles Varèse was a French composer who spent the greater part of his career in the United States. Varèse's music emphasizes timbre and rhythm; he coined the term "organized sound" in reference to his own musical aesthetic. Varèse's conception of music reflected his vision of "sound as living matter" and of "musical space as open rather than bounded". He conceived the elements of his music in terms of "sound-masses", likening their organization to the natural phenomenon of crystallization. Varèse thought that "to stubbornly conditioned ears, anything new in music has always been called noise", and he posed the question, "what is music but organized noises?"