Interpersonal musical entrainment—temporal synchronization and coordination between individuals in musical contexts—is a ubiquitous phenomenon related to music’s social functions of promoting group bonding and cohesion. Mechanisms other than sensorimotor synchronization are rarely discussed, while little is known about cultural variability or about how and why entrainment has social effects. In order to close these gaps, we propose a new model that distinguishes between different components of interpersonal entrainment: sensorimotor synchronization —a largely automatic process manifested especially with rhythms based on periodicities in the 100–2000 ms timescale—and coordination , extending over longer timescales and more accessible to conscious control. We review the state of the art in measuring these processes, mostly from the perspective of action production, and in so doing present the first cross-cultural comparisons between interpersonal entrainment in natural musical performances, with an exploratory analysis that identifies factors that may influence interpersonal synchronization in music. Building on this analysis we advance hypotheses regarding the relationship of these features to neurophysiological, social, and cultural processes. We propose a model encompassing both synchronization and coordination processes and the relationship between them, the role of culturally shared knowledge, and of connections between entrainment and social processes.

In a classic study, Fraisse (1956) demonstrated that sequences of four sounds defining three different interval durations exhibit characteristic distortions in reproduction: The two more similar intervals tend to be assimilated to each other, resulting in a rhythm containing just two interval durations. The present study examined whether highly trained musicians (including percussionists) are able to perform such rhythms accurately in a synchronization-continuation tapping paradigm. Eleven rhythms, a subset of those used by Fraisse, were presented cyclically at his original tempo and also at a slower tempo. The musicians produced significant rhythm distortions, though they were smaller than those observed by Fraisse and not always assimilative. They were relatively larger at the fast than at the slow tempo and occurred in both synchronization and continuation. In contrast to Fraisse’s data, the most variably reproduced target rhythm was the one in which the two longer intervals were identical. The pattern of distortions suggested attraction towards ideal rhythms in which all three interval durations are different, representing metrical categories with nominally simple interval ratios (some permutation of 1:2:3) that were probably activated by the cyclic presentation of the rhythms. However, these attractors themselves seemed to be somewhat distorted, perhaps reflecting the simultaneous presence of a nonmetrical attractor that differentiated two interval categories regardless of ratio, as observed by Fraisse.

when rhythms consisting of two unequal intervals are reproduced cyclically, their interval ratio tends to be distorted in the direction of 1:2 (= 0.5), which thus seems to function as an “attractor ratio” (AR). However, recent results for musicians in a synchronization task (Repp, London, & Keller, 2011) have suggested an upward-shifted AR (USAR) somewhat greater than 0.5. Three new experiments suggest that this shift is not due to synchronization versus continuation tapping, the range of interval ratios employed, unimanual versus bimanual tapping, intensity differences between taps, or mental subdivision of the long interval, although some of these factors may affect its size. The new results also show that the USAR is found more consistently in musicians than in nonmusicians and seems to arise in rhythm production, not in perception. While the exact causes of the USAR remain unclear, the results suggest that the AR is not necessarily the mathematically simplest interval ratio.

while spontaneity is often a desirable quality in music performance, the objective musical features that characterize genuinely spontaneous performances are unclear. We addressed this issue by recording pianists’ keystroke intensity and timing as they produced improvised jazz solos and rehearsed imitations of these solos. Results indicated that the entropy of keystroke intensity was reliably highest for improvisations. Corresponding effects for timing were less consistent. The effects observed for intensity may reflect irregularities in force control associated with relatively wide variations in the performer’s (un)certainty about upcoming actions during real-time musical invention. Related fluctuations in loudness may provide listeners with cues to musical spontaneity, thereby affecting aesthetic evaluations of performance quality.

This work investigates how spatial and temporal aspects of rhythmic movements are affected by spatial and temporal components of a visual pacing sequence. Participants synchronized finger taps with three visual pacing sequences ( Flash , High Finger , and Low Finger ) at two tempi (500 ms and 400 ms interonset interval). The Flash sequence contained only temporal information, whereas the two Finger sequences contained apparent motion of different amplitudes. Participants' finger movements were recorded with a motion capture system, and movement trajectories and timing accuracy were analyzed. Results indicated that apparent motion facilitates visuomotor synchronization accuracy, which likely stems from tight perception-action links. Stimulus amplitude modulated tap amplitudes in the same direction, but this spatial assimilation did not adversely affect timing accuracy. Flexion times toward the target were significantly shorter than extension or dwell times, and could indicate a relatively ballistic movement trajectory. Local deviations of tap timing correlated with the movement trajectories from the preceding and following movement cycle. For example, after a late tap, the following movement cycle had lower amplitude and shorter extension and dwell times. This could signify the workings of error correction mechanisms that ensure stable synchronization.

The Role of Anticipatory Auditory Imagery in musical ensemble performance was investigated by examining the relationship between individual differences in auditory imagery and temporal coordination in piano duos. Vividness of imagery for upcoming sounds was assessed in 14 pianists using a task that required the production of rhythmic sequences with or without auditory feedback. Ensemble coordination was assessed by examining temporal relations between body movements (recorded by a motion capture system) and sound onsets (triggered by key strokes on two MIDI pianos) in seven duos playing two contrasting pieces with or without visual contact. Sound synchrony was found to be related to anterior-posterior body sway coordination in a manner that depended upon leader/follower relations between pianists assigned to 'primo' and 'secondo' parts. Furthermore, the quality of coordination, which was not affected markedly by whether pianists were in visual contact, was correlated with individual differences in anticipatory auditory imagery. These findings suggest that auditory imagery facilitates interpersonal coordination by enhancing the operation of internal models that simulate one's own and others' actions during ensemble performance.

PHASE CORRECTION, WHICH IS NECESSARY for synchronization of movements with a rhythm, has been studied primarily with isochronous sequences.We used a phase perturbation method to examine phase correction in synchronization with nonisochronous sequences (3:2 interval ratios), using musically trained participants. In isochronous control sequences, the phase correction response (PCR) of the tap following a small phase shift was larger when the intervals were long (600 ms) than when they were short (400 ms). In nonisochronous cyclic two-interval patterns, we found a similar dependence of the PCR on the duration of the interval following a phase shift. In three-interval patterns, however, there was no clear dependence on interval duration. The metrical interpretation of the sequences (downbeat location) had no effect on phase correction. In general, phase correction was as effective with nonisochronous as with isochronous sequences.

THIS STUDY EXAMINED PRODUCTION and synchronization of eight uneven rhythms (set A: 2+3, 3+2; set B: 2+2+3, 2+3+2, 3+2+2; set C: 2+3+3, 3+2+3, 3+3+2) at rates that made it difficult to subdivide the component intervals into elementary metrical pulses. The main questions were how interval ratios would change as a function of tempo within this range, and whether metrical downbeat location (which distinguishes the rhythms within each set) would be reflected in any of the dependent measures. Musically trained participants tapped each rhythm cyclically in synchrony with an auditory template and then continued to tap in three ways: self-paced, paced by a sequence of downbeats, or paced by a rapid stream of isochronous subdivisions. Each task was carried out at eight tempi. The third task assessed the temporal limit of subdivision for these rhythms (about 6 Hz), which was exceeded by most tempi. Results showed that the mean long––short (3:2) interval ratio was already larger than 1.5 at the slowest tempo in rhythm sets A and B, and increased with tempo in sets B and C, but did not approach 2. Uneven rhythms thus can be produced without mental subdivision, but only with substantial enhancement of the contrast between long and short intervals. Metrical downbeat location had no reliable effect on interval ratios but was reflected in more forceful downbeat taps and in different alignments of taps with a pacing sequence. In general, effects of temporal grouping (between rhythm sets) outweighed those of metrical interpretation (within rhythm sets).

Performing in musical ensembles can be viewed as a dual task that requires simultaneous attention to a high priority �target� auditory pattern (e.g., a performer�s own part) and either (a) another part in the ensemble or (b) the aggregate texture that results when all parts are integrated. The current study tested the hypothesis that metric frameworks (rhythmic schemas) promote the efficient allocation of attentional resources in such multipart musical contexts. Experiment 1 employed a recognition memory paradigm to investigate the effects of attending to metrical versus nonmetrical target patterns upon the perception of aggregate patterns in which they were embedded. Experiment 2 required metrical and nonmetrical target patterns to be reproduced while memorizing different, concurrently presented metrical patterns that were also subsequently reproduced. Both experiments included conditions in which the different patterns within the multipart structure were matched or mismatched in terms of best-fitting meter. Results indicate that dual-task performance was best in matched-metrical conditions, intermediate in mismatched-metrical conditions, and worst in nonmetrical conditions. This suggests that metric frameworks may facilitate complex musical interactions by enabling efficient allocation of attentional resources.