The original title of Hans Richter’s Rhythmus 21 (completed in 1924) was Film Is Rhythm. And it is the rhythmic interplay of black, white and gray rectangles and squares that creates the basis of this early example of so-called pure or absolute film. At precisely stipulated intervals, the geometric elements grow and vanish, skip or roam around the screen; white merges into black and vice versa, with the rectangular screen acting as a kind of orchestral framework. For his rhythmically structured animation, Richter made use of paper rectangles and squares and also used the film negative as a positive. In its continuous modification of abstract shapes, Rhythmus 21 reveals a musicality of the moving image that is completely anchored in dynamics, in the interaction and opposition between the geometric figures that are used.