Towards a calculus for expressive timing in music

This paper presents a calculus that enables expressive timing to be transformed on the basis of the structural aspects of the music. Expression within a unit is defined as the deviations of its parts with respect to the norm set by the unit itself. The behaviour of musical material under expressive transformations is determined uniquely by its structural description and the type of expression. Although the calculus separates different kinds of behaviour, it entails no musical knowledge of the transformations themselves and it also does not model music cognition. The algorithmic simplicity of the calculus combined with its elaborate knowledge representation mirrors the common hypothesis that the complex expressive timing profiles found in musical performances can be explained as the product of a small collection of simple rules linked to a relatively complex structure. The calculus will hopefully prove to be a solid basis for formalised theories of music cognition.