The parsing of undifferentiated tone sequences into groups of qualitatively distinct elements is one of the earliest rhythmic phenomena to have been investigated experimentally ( Bolton, 1894 ). The present study aimed to replicate and extend these findings through online experimentation using a spontaneous grouping paradigm with forced-choice response (from 1 to 12 tones per group). Two types of isochronous sequences were used: equitone sequences, which varied only with respect to signal rate (200, 550, or 950 ms interonset intervals), and accented sequences, in which accents were added every two or three tones to test the effect of induced grouping (duple vs. triple) and accent type (intensity, duration, or pitch). In equitone sequences, participants’ grouping percepts ( N = 4,194) were asymmetrical and tempo-dependent, with “no grouping” and groups of four being most frequently reported. In accented sequences, slower rate, induced triple grouping, and intensity accents correlated with increases in group length. Furthermore, the probability of observing a mixed metric type—that is, grouping percepts divisible by both two and three (6 and 12)—was found to be highest in faster sequences with induced triple grouping. These findings suggest that lower-level triple grouping gives rise to binary grouping percepts at higher metrical levels.

W hile syncopation generally refers to any conflict between surface accents and underlying meter, in rock and other recent popular styles it takes a more specific form in which accented notes occur just before strong beats. Such “anticipatory” syncopations suggest that there is an underlying cognitive representation in which the accented notes and strong beats align. Syllabic stress is crucial to the identification of such syncopations; to facilitate this, we present a corpus of rock melodies annotated with lyrics and syllabic stress values. We propose a new measure of syncopation that incorporates syllabic stress; we also propose a measure of anticipatory syncopation, and show that it reveals a strong presence of this type of syncopation in rock music. We then use these measures to explore other aspects of syncopation in rock, including its occurrence in different parts of the 4/4 measure, its dependence on tempo, its historical evolution, and its aesthetic functions.