Open Form

Open Form is a term coined by Earle Brown in the 1950s to describe works where the structure and form of the piece was left open to interpretation by the composer while the materials (notes, rhythms, etc.) were pre-composed. Brown's early experiments in this area were extreme and abstract—a collection of works titled "FOLIO and FOUR SYSTEMS" are emblematic of his initial experiments.

Over his career, he developed an approach to Open Form that integrated unique approaches to modularity in form that he compared to the mobiles of Alexander Calder. Within this framework, bits of music would be composed as numbered or cued "events" and grouped into "pages". Events could be superimposed within a single page, played at different speeds, etc. and one could navigate through a work at varying paces, returning to previous pages, skipping forward, backward, etc. In each work, a slightly different approach was taken, but this general logic of modularity remained.

Anthony Braxton has developed these ideas in his own way, integrating even greater multiplicity and laying in his Ghost Trance Music structures within which secondary and tertiary compositions may become overlaid by the performers.

Walter Thompson has extended these ideas through a vast language of conducting gestures called soundpainting.

John Zorn extended these ideas in his game pieces, most famously in Cobra.