Watching live dance, theatre, or music events is an inherently social activity in which people often share a highly emotional experience. Yet, neuroscientific research into music or dance cognition has been almost exclusively conducted on individual people in a lab setting. Across three live performances of a contemporary dance choreography we measured real-time dynamics between the brains of large audience groups while watching the show. We recorded 32-channel mobile EEG and respiratory activity from up to 23 audience members simultaneously (total N = 69) and assessed the spectators’ engagement after the performance. We computed inter-brain correlations to measure brain synchrony between audience members relative to an active resting-state baseline. Audience EEG synchrony was highest in the delta frequency band and varied with the structural features of the choreography: sections with greater movement complexity and direct audience interaction (‘breaking the fourth wall’) showed significantly higher synchrony than resting-state and were rated significantly higher for engagement by an independent audience sample. Granger Causality analyses showed that the dancers’ movements and the choreographer’s intention to direct collective attention were the best predictors of delta band synchrony over time, outperforming changes in music or lighting. Our findings show that audience engagement during a live performance is measurable as artistically directed, collective attention between co-present spectators.