In 1958, guitarist Jim Hall, in notes to a Jimmy Giuffre record, used the term instant composition to describe improvising. A few years later, Misha Mengelberg, knowing nothing of this, recoined the term, and it stuck. A quiet manifesto, those two English words countered notions that improvising was either a lesser order of music-making than composing, or an art without a memory, existing only in the moment, unmindful of form. Misha's formulation posited improvisation as formal composition's equal (if not its superior, being faster).
Yes but: Misha says he was thinking of instant coffee, stuff any serious java drinker (count Misha in: espresso cup rattling in its saucer announces his approach to a stage) recognized as a sham substitute, however aggressively sold. He deflates his lofty idea even as he raises it. He's also praised the instant poetry that came out of the Fluxus art movement he was involved with around then: put individual words on strips of paper, place in a jar and shake. Years later it became a commercial novelty: words on tiny magnetic tiles you can arrange on a refrigerator door.
For Misha mid-'60s Fluxus was inviting because it stood for nothing, had no ideals to defend. What bound together Fluxus's conceptualists, shock artists, early minimalists, musical comics et cetera was a need for a performance format that could accommodate them all. One solution was that symbol of '60s kookiness, the multimedia Happening. Those events belatedly helped inspire Mengelberg's absurdist-circus theater shows with Wim T. Schippers in the '70s and '80s, and the fluid play of styles, unbinding rules, lyricism and barnyard humor that characterize the ICP Orchestra today.