Pachet et al. Representing temporal musical objects in the MusES system, Journal of New Music Research, 25:3, 252-75 1996 Representing temporal musical objects and reasoning in the MusES system François Pachet, Geber Ramalho and Jean Carrive LAFORIA-IBP, Université Paris 6, Boîte 169, 4, Place Jussieu, 75252 Paris, France. E-mail: pachet@laforia.ibp.fr ABSTRACT. We describe a representation framework for temporal objects and reasoning in the MusES system. The framework is claimed to be use-neutral within the context of tonal music. It is based on the use of an object-oriented programming language, Smalltalk, and makes full use of two main representation mechanisms: class inheritance and delegation. We describe the kernel of the representation framework and explain the main design choices. We show how the kernel can be used and extended to represent important temporal concepts related to tonal music. The framework is validated by the realization of two substantial applications: an automatic analyser for chord sequences, and a simulator of jazz improvizations. 1. Introduction 1.1. OOP and musical knowledge representation Object-Oriented Programming (OOP) has traditionally been a favorite paradigm to build complex musical systems (see e.g. the special issue of the Computer Music Journal, 13 (2), 1989 on the use of Smalltalk for musical systems). This adequacy of object-oriented programming to musical representation has given birth to an impressive list of famous musical systems: the Formes system, to specify interacting concurrent musical processes (Cointe & Rodet 1991), the MODE system, a environment for the development of tools for musical score, sound processing and performance (Pope 1991), the Kyma system, a graphic environment dedicated to digital audio processing and computer-aided composition (Scaletti 1987), and more recently Improvisation Builder, a framework for simulating jazz improvisation, seen as a particular kind of communication between agents (Walker et al., 1992). Following this movement, we are deeply convinced that the structures and mechanisms of object-oriented programming are particularly well suited for effective musical knowledge representation. We conducted a series of experiments aiming at studying more particularly the representation of knowledge related to tonal music. These experiments are embodied in a system called MusES [Pachet 94]. The MusES system contains a representation of the basic concepts of tonal harmony such as pitch classes, notes, intervals, chords, scales, and melodies. An important claim underlying the MusES effort is that it is possible to provide a use-neutral representation, within the context of tonal music. By use-neutral, or application-independent, we mean that these representations may be used by specific applications as is, with only minor modifications if any. This claim is backed up by the philosophical assumption that there exist some common sense layer of musical knowledge which may be made explicit. We will not discuss the validity of this hypothesis here, and will take it for granted in the context of this paper.