This article examines collaborative mathematical tasks that entail sympathetic coordinated movements. We discuss the affective bonds that form when students participate in such tasks. Using Maxine Sheets-Johnstone's term "affectivity" to characterize the responsive nature of bodies, we analyse data from a teaching experiment where students collaboratively explore the dynamic aspects of mathematical figures. We work with the ancient Greek concept of 'sympathy' to study the complex ways that multi-body assemblages actively coordinate their movements in the midst of a mathematical task. We include here diverse kinds of often imperceptible body movement (gesture, face, eye, foot, etc), and discuss how mathematical concepts are assembled through such movements. Our analysis bridges three scales: (1) the micro-phenomenological scale of the pre-individual affect, (2) the individual scale of human movement, and (3) the transindividual scale of collective endeavours.