One of the paradoxes of the radical music is that it thrives at both extremes, at densities both close to zero and at or past the point of any perceivable order or distinction among constituent parts. A further paradox here is that, on the one hand, an ever-lower limit on materials or methods can create ever-more mysterious and inscrutable musical objects and processes while, on the other hand, ever-more densely overlaid materials and complicated procedures can lead to sum totals which are heard as ever-more elementary surfaces or gestalts. YET A FURTHER PARADOX is that composing under ever-more narrow restrictions or limits may yield ever-larger numbers of possible realizations while a lack of limits may force a composition into a density that is essentially ergodic in nature.
Among composers, John Cage and James Tenney were perhaps most focused on these paradoxes, composing at both limits, but the concern is widespread: much of the music of Nancarrow and Ligeti depends on it, Alvin Lucier's string quartet, Navigations for Strings or La Monte Young's Well-Tuned Piano feature it. Heck, Monteverdi's concitato style and Berlioz's use of spatial polyphony with very restricted pitch materials and even the Javanese irama system, coordinating material density with tempi, depend upon it, too. And, outside of music proper, the productive use of restrictions are extremely interesting: the Oulipo, of course, or the fiction of Walter Abish, the Dogme 95 films, or even the Mundane Science Fiction movement are all good examples that limitations can focus and form work but are not necessarily limiting.