In this Chapter, various key theories and ideas about rhythm, composition, structure and metre will be examined, in particular, those theories of rhythm that have been proposed by Western thinkers who refer to ancient Greek conceptions of rhythm and metre, and to its visual counterpart: structure or schema. Scanning the diversity of theories of rhythm, schema and metre in order to trace transitions in the definition of rhythm as they might emerge in historical order is not the intention here. In the interests of clarity, however, it is often necessary to maintain a degree of critical distance with respect to the specific theories of rhythm of other thinkers. As we have seen, Mondrian theorised and worked on the basis of his own original ideas, and in that sense was somewhat distanced from the ideas of other theorists engaged in the visual field. Conceptually, I do not subscribe to theories of rhythm which are identified with metre or tempo (or a series of pulses). Following Mondrian, I am dissatisfied with the notion of rhythm being based on regular movement (repetition) or a sequence of notes or equivalent visual elements. Conceptually and philosophically, I regard rhythm as structure (schema) or composition. Empirically, in terms of the audience or viewer's volition, I consent to concur with the necessity for metre and a certain degree of repetition (or a sequence of auditory or visual elements). This is not rendered in terms of a manifest sense (auditorily or visually), but, rather, in terms of a mental or internalised sense.