People move to music and coordinate their movements with others spontaneously. Does music enhance spontaneous coordination? We compared the influence of visual information (seeing or not seeing another person) and auditory information (hearing movement or music or hearing no sound) on spontaneous coordination. Pairs of participants were seated side by side in rocking chairs, told a cover story, and asked to rock at a comfortable rate. Both seeing and hearing the other person rock elicited spontaneous coordination, and effects of hearing amplified those of seeing. Coupling with the music was weaker than with the partner, and the music competed with the partner's influence, reducing coordination. Music did, however, function as a kind of social glue: participants who synchronized more with the music felt more connected.