New Complexity
At the time of its completion, it was possibly the most technically demanding solo piano work in existence due, for the most part, to its extreme length and rhythmic complexity and to the vast resources of physical and mental stamina demanded by its many passages of transcendental virtuosity, although some works conceived by New Complexity, modernist and avant-garde composers, along with Sorabji himself, were more difficult still; it is in this particular area that "Opus clavicembalisticum" primarily receives its notoriety, and to this day is still highly regarded in that light.