Generative Rules for Music Performance: A Formal Description of a Rule System

Abstract

This is a detailed technical presentation of performance rules resulting from a project in which music performance has been analyzed by means of an analysis-by-synthesis procedure (Sundberg et al. 1983). The rules have been developed in cooperation with Johan Sundberg and Lars Fryd6n. Lars Fryd6n is the musical expert, Johan Sundberg has contributed mostly to the cognitive aspects and, in an early stage of the project, to programming, and the author has been responsible for the organization and formulation of the final programming. The project has been extensively described and discussed in previous articles (see References). The purpose of the rules is to convert the written score, complemented with chord symbols and phrase markers, to a musically-acceptable performance. They are currently implemented in the programming language Lisp on a Macintosh computer (Friberg and Sundberg 1986) and the software is available on request. The rules operate on the parameters listed in Table 1. Two different tone articulation models are used. The first model uses only off-time duration (DRO), as defined in Fig. 1. The second model is more complete and uses a four-point envelope (T1-T4 and LI-L4) to shape each tone individually (see Fig. 16). Whenever possible, the resulting deviations from the rules are additive. This means that each tone may be processed by several rules, and the deviations made from each rule will be added successively to the parameters of that tone. The order in which the rules are applied is in general not critical except for the synchronization rules and the amplitude envelope rules which have to be applied last. The mixed intonation rule must also be applied after all other intonation rules. The sound parameters that are manipulated by the rules are listed in Table 1. For technical reasons, the rules will be presented in this article in an order based on the resulting parameter changes. There are five groups of rules: (1) single parameter rules,