Open form A great deal of Brown's work is composed in fixed modules (though often with idiosyncratic mixtures of notation), but the order is left free to be chosen by the conductor during performance. The material is divided in numbered "events" on a series of "pages". The conductor uses a placard to indicate the page, and with his left hand indicates which event is to be performed while his right hand cues a downbeat to begin. The speed and intensity of the downbeat suggests the tempo and dynamics. Brown's first open-form piece, Twenty-Five Pages, was 25 unbound pages, and called for anywhere between one and 25 pianists. The score allowed the performer(s) to arrange the pages in whatever order they saw fit. Also, the pages were notated symmetrically and without clefs so that the top and bottom orientation was reversible. Through this procedure, no two performances of an open form Brown score are the same, yet each piece retains a singular identity and his works exhibit great variety from work to work. Brown relates his work in open form to a combination of Alexander Calder's mobile sculptures and the spontaneous decision making used in the creation of Jackson Pollock's action paintings. Notation Although Brown precisely notated compositions throughout his career using traditional notation, he also was an inventor and early practitioner of various innovative notations. In Twenty-Five Pages, and in other works, Brown used what he called "time notation" or "proportional notation" where rhythms were indicated by their horizontal length and placement in relation to each other and were to be interpreted flexibly. However, by Modules I and II (1966), Brown more often used stemless note heads which could be interpreted with even greater flexibility. In 1959, with Hodograph I, Brown sketched the contour and character abstractly in what he called "implicit areas" of the piece. This graphic style was more gestural and calligraphic than the geometric abstraction of December 1952. Beginning with Available Forms I, Brown used this graphic notation on the staff in some sections of the score. December 1952 and FOLIO December 1952 is perhaps Brown's most famous score. It is part of a larger set of unusually notated music called FOLIO. Although this collection is misconstrued as coming out of nowhere historically, music notation has existed in many forms—both as a mechanism for creation and analysis. Brown studied what is now called Early Music, which had