Music Between Two Minds: Individual Signatures, Shared States, and the Emergence of Creative Interaction
Some of the most valued forms of human creativity arise between people-in conversation, collaboration, and improvised music-yet how two minds jointly regulate the flow of novelty in real time remains unknown. Here we examined the information dynamics of interpersonal improvisation using 986 professional jazz improvisations. Pitch-based fluctuations of uncertainty and surprise behaved as signatures of individual identity: the two partners differed within 90% of takes, performers were identifiable from single solos and the separation between partners persisted undiminished across turns and takes. Rhythm-based fluctuations showed the reverse organization: partners were statistically indistinguishable within a take yet shifted together from take to take, and this shared state drifted gradually as each performance progressed, with each performer moving away from their own past at the same rate as from their partner's. Beyond joint drift, solo hand-offs revealed turn-by-turn complementarity: when one performer exceeded their own average surprise in the predictive dynamics of improvisation, the partner's next solo fell below their own, in both pitch and rhythm and in all duos. Improvising pairs thus neither fuse into one system nor remain two independent ones: they preserve individual melodic voices while sharing a rhythmic state, within which moment-to-moment push-pull continually rebalances their interaction. Individuality and togetherness thus coexist, carried by different musical dimensions, a measurable organization of creativity that emerges between minds.