Scores, Programs, and Time Representation: The Sheet Object in OpenMusic

Current computer-music systems deal with complex processes related to heterogeneous musical contents and information. In particular, the objects involved in music composition correspond to various temporal paradigms and representations. For instance, contemporary music composers frequently deal with time durations, or even directly with the continuous aspects of sound structures, instead of (or in relation to) a traditional pulsed-time representation. In these cases, however, continuous musical material must generally be associated with discrete and symbolic structures to allow for their meaningful representation (Boulez 1987). The score is a general framework for music writing in which this integration of musical material and the related issues of time representations should be carefully considered. Regardless of whether it concerns instrumental or electro-acoustic music, this document is of major importance as a formal support and a preferred place for musicians to write, read, and think about music.

In this article, we focus on this notion of the score in computer-aided composition (CAC) through a presentation of related work in the visual programming environment OpenMusic (Agon 1998; Assayag et al. 1999). We introduce a new object recently created in OpenMusic: the sheet. This new object gathers results of CAC experiments and research concerning the relations between programs and score representations, the integration of sound and signal processing in compositional processes, the mixing of heterogeneous temporal systems, and the general visual representation of time structures in music notation. The sheet editor allows for accurate rhythmic notation while integrating specific features such as the support for new types of musical objects and programming tools.

After a brief discussion of the question of the score in computer music composition, we present previous attempts at combining programs and scores in OpenMusic. The sheet editor is then presented. Its main features, which are detailed next, concern the common representation of musical objects related to heterogeneous time systems and the capability to develop programs from within the score. We then examine the possible function of this new object in the general CAC framework, and we conclude with a concrete example with the reconstitution of an excerpt from a score by Karlheinz Stockhausen.

Computer-Music Scores

Traditional musical categories are being deconstructed by contemporary musical practices and computer-composition tools. The nature and the role of the score has thus to be considered from a renewed point of view.

The concept of the score usually refers to a music representation built on a notation system inherited from the Western music tradition, which is basically a compound graphical structure used to organize musical events (notes) in time. More generally, it can be seen as a place where the composer writes music in terms of a standard and universal language describing some musical parameters or instructions to perform in order to produce sound. In this sense, computer-composition tools commonly call any document containing a list or sequence of such parameters or commands a “score.” In principle, this kind of score is not always intended to be read by human performers and thus does not systematically meet high-level symbolical requirements. It can be represented with simple numerical data, then converted to synthesis parameters or to symbolic notation for performance.

Our position, however, is to reaffirm the need for symbolic musical representations in computer system scores. As mentioned previously, a score is not a simple sequence of instructions but also a fundamental medium for composers to think about their music, to describe and communicate musical forms and structures according to a symbolic representation system. It supports and informs the underlying compositional intentions.

This notion of score can therefore be a problematic point, particularly in the context of electro-acoustic music (Ebbeke 1990). The questions of how an electro-acoustic score should be notated and interpreted, which are the objects of various research projects in the musicological and signal-processing communities, are not the object of our current discussion. It is important to comment, however, that these notions are getting closer, and even sometimes tightly integrated into, the compositional process: Composers now create their own instruments using sound-synthesis languages and invent their own...