Acting together beyond synchrony: Event-dependent alignment of breathing in an expert musical ensemble.

Joint musical performance is a paradigmatic form of joint action, requiring multiple performers to coordinate their actions toward a shared goal across differentiated roles. Physiological synchrony and related forms of coupling have been examined as correlates or supporting processes of such coordination. The present study investigated interpersonal breathing dynamics in nagauta-bayashi, a traditional Japanese musical ensemble characterized by long intervals between structurally defined musical events, differentiated instrumental and functional roles, and the absence of a conductor. Respiratory activity was recorded using wearable sensors from six professional performers within an 11-member ensemble during two consecutive takes of the same musical excerpt. We analyzed inter-performance and inter-performer similarities in breathing patterns, as well as event-related respiratory changes around komi, a performer-recognized coordination event used to manage temporal spacing and transitions. The results showed that breathing patterns were reproducible within individuals across takes, including players whose breathing does not directly generate instrumental sound. In terms of interpersonal breathing coordination, the data did not provide evidence for sustained lag-zero breathing synchrony over extended segments. In contrast, event-related analyses revealed a transient, ensemble-level alignment of inhalation immediately following komi events across measured performers. These findings suggest that respiratory coordination in the present nagauta-bayashi ensemble was organized as stable intra-individual respiratory patterns alongside transient, event-dependent interpersonal alignment. By demonstrating this temporally structured organization in an ecologically grounded, role-differentiated performance context characterized by sparse coordination landmarks, the study provides case-specific empirical support for dynamic accounts of joint action without presupposing sustained synchrony as the primary organizing principle.