Over the last 2 decades much work has been done on the nature of expression in musical performance. Expression, which takes the form of subtle transformations of timing, dynamics, pitch and timbre, etc., may be measured fairly accurately when a score-based representation is available. It is generally agreed that the major function of expression in these cases is the communication of the performer's structural/motional interpretation of the piece being performed. Indeed, it is possible to demonstrate that the greater part of expressive variation may be accounted for by the two major components of rhythmic structure, namely, meter and grouping. However, little attention has been paid as to how the perception of rhythm may be influenced by expression. In this paper the perception of rhythm in expressive performance is reviewed from the point of view of a recent auditory-motor theory of rhythm perception [N. P. Todd and G. J. Brown, ``Vizualization of rhythm, time and metre,'' Artificial Intelligence Rev. (1996)]. The similarity between musical performance and the prosody of poetry recital is also discussed in light of a recent experiment to test the behavior of the model with speech. This is consistent with the view that rhythmic expression has a common origin in music and speech.