"Sync or Swarm" provides a fascinating study of musical improvisation, using theories from cultural and cognitive studies and the emerging sciences. Musical improvisation hinges on one's ability to synchronize intention and action and to maintain a keen awareness of, sensitivity to, and connection with the evolving group dynamics and experiences. The most successful improvisations are those in which the musicians are able to synchronize, not necessarily their sounds - although this too can miraculously happen - but their intentions or their moments of inspiration. And even during the most complex and dense passages of collective improvisation, a swarm-like quality can emerge in which individual parts are moving in very different directions and yet the musical whole moves with a collective purpose. David Borgo presents a systemic view of improvisation, with individual chapters funneling outward in scope: from the perspective of a solo improviser (English saxophonist Evan Parker), to that of a group interacting in performance, to the long-term dynamics of an improvising group from formation to dissolution, and finally regarding the network dynamics that bind together improvisers and groups into an aesthetic community. Each of these chapters is paired with a different aspect of the emerging sciences - including perspectives from cognitive science, biology, chaos and complexity theories, and the study of social networks - in order to offer new ways of engaging with and shaping the discourses that surround music in general and improvisation in particular.