A theoretical model is introduced, by the aid of which descriptions of sequential and concurrent processes may be built taking account of the sophistication and generality of contemporary musical concepts. This is achieved through an independent and unrestricted mapping between physical time and a symbolic set of dates. Sequential structures are considered first, then the nature of this mapping and its practicle implementation in a real-time synthesizer are discussed. Polymetric structures are introduced and a method is outlined for mapping events to symbolic dates when concurrent processes are incompletely described.