Humans are exquisitely sensitive to social interactions. This study explored whether this extends to interactions in music performance. Jazz musicians are fluent at working together to produce music that is more than the sum of its parts, and listeners claim anecdotally to hear when musicians are ‘in the groove’. We employed jazz-standard duets varying in the opportunity for collaboration (two-way, one-way, none), to test listeners’ perception of collaboration. In experiment 1, participants rated random selections from these recordings in the dimensions of synergy, creativity, emotionality, and engagement. Results showed considerable sensitivity to collaboration, with sensitivity varying both with social intelligence and musical training of the participant. In experiment 2, participants made explicit judgments of whether the selections involved collaboration, with the results showing they could not. We conclude that the degree of collaboration in joint musical performances influences the implicit experience of listeners, but is not accessible for explicit judgments.