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Patterns of coordination in simultaneously and sequentially improvising jazz musicians

In Joint Action (JA) tasks, individuals must coordinate their actions so as to achieve some desirable outcome at the grouplevel. Group function is an emergent outcome of ongoing, mutually constraining interactions between agents. Here we investigate JA in dyads of improvising jazz pianists. Participants’ musical output is recorded in one of two conditions: a real condition, in which two pianists improvise together as they typically would, and a virtual condition, in which a single pianist improvises along with a “ghost partner” – a recording of another pianist taken from a previous real trial. The conditions are identical except for that in real trials subjects are mutually coupled to one another, whereas there is only unidirectional influence in virtual trials (i.e. recording to musician). We quantify ways in which the rhythmic structures spontaneously produced in these improvisations is shaped by mutual coupling of co-performers. Musical signatures of underlying coordination patterns are also shown to parallel the subjective experience of improvisers, who preferred playing in trials with bidirectional influence despite not explicitly knowing which condition they had played in. These results illuminate how mutual coupling shapes emergent, group-level structure in the creative, open-ended and fundamentally collaborative domain of expert musical improvisation.