When a good fit is not good enough: A case study on the Final Ritard
Henkjan Honing

Abstract:
The relation between music and motion has been a topic of much
theoretical and empirical research.  An important contribution is made
by a family of computational theories, so-called kinematic models,
that make an explicit relation between the laws of physical motion in
the real world and expressive timing in music performance (see Friberg
& Sundberg, 1999). These models were shown to have a good fit
with a variety of empirical data, most notably that of the final
ritard in music performance: the typical slowing down at the end of a
music performance. However, the predictions of these kinematic models
are independent of (1) the number of events, (2) the rhythmic
structure, and (3) the overall tempo of the performance; These factors
have no effect on the predicted shape of the ritardando. Computer
simulations of a number of rhythm perception models show, however, a
large effect of these structural and temporal factors.  They are
therefore proposed as a perception-based alternative to the kinematic
approach. While a final ritard might coarsely resemble a square root
function (according to a kinematic model), the predictions made by
perception-based models are also influenced by the temporal structure
of the musical material that constraints possible shapes of the
ritard, and it can therefore be considered a potentially stronger
theory than one that simply has a good fit (Roberts & Pashler,
2000).