Detectability of uneven rhythms

Hans-Henning Schulze

Philipps Universität Marburg, Germany

In danubian dances uneven subdivisions which are close to one (e.g. 3:7, 7:16) are common and give the music its flavor. Also, in performed classical music and jazz performances subtle deviations from equal subdivisions are used for expressive purposes. The question addressed in this paper is, how easy it is for the listener to detect these deviations. The task of the subjects is to judge, in a forced choice setting, which of two rhythmic patterns is uneven. The amount of unevenness is changed adaptively, depending upon the correctness of the judgment. The changes of level follow a psychophysical procedure developed by Kärnbach. It converges to a level in which the probability of a correct response is .75. The period of the patterns is randomized from trial to trial. The number of periods presented is an important factor of the experiment. The improvement of the detectability with the number of periods presented will be modeled by a mechanism of information integration over time.