Rhythm belongs with harmony, melody and timbre as one of the most fundamental aspects of music. Sound by its very nature is temporal, and in its most generic sense, the word \textit{rhythm} is used to refer to all of the temporal aspects of a musical work, whether represented in a score, measured from a performance, or existing only in the perception of the listener. In order to build a computer system capable of intelligently processing music, it is essential to design representation formats and processing algorithms for the rhythmic content of the music. Computer systems reported in the literature offer different interpretations of the words ``automatic rhythm description'' as they address diverse applications such as tempo induction, beat tracking, quantisation of performed rhythms, meter induction and characterisation of intentional timing deviations. Although some rhythmic concepts are consensual, no single representation of rhythm has been devised which would be suitable for all applications. In this paper, we propose a unifying framework for automatic rhythm description systems, and review existing systems with respect to the functional units of the proposed framework.

This research was supported by the EU project FP6-507142 (SIMAC) and the national project Y99-INF sponsored by the Austrian Federal Ministryu of Education, Science and Culture in the form of a Start Research Prize. The Austrian Research Institute for Artificial Intelligence acknowledges the support of the Austrian Federal Ministries of Education, Science and Culture and of Transport, Innovationa and Technology.