Improvising music involves a leap into the uncharted, but its success relies on abilities honed through experience and on an unwavering commitment to the moment and context of performance. Improvisers synchronize their intentions and actions, all the while maintaining a keen sensitivity to and connection with the evolving group dynamic. At times, performance can evoke a swarm like quality in which the individual parts are moving in very different ways, yet the musical whole evolves with a collective purpose. "Sync or Swarm" provides a fascinating study of musical improvisation, using theories from cultural and cognitive studies and the emerging science of chaos and complexity. David Borgo explores his topic with a systems approach, as individual chapters expand outward in scope: from the perspective of a solo improviser (English saxophonist Evan Parker); to that of a group interacting in performance and over time (the Sam Rivers trio); to the network dynamics that bind together performers, listeners, educators, and promoters into a musical community. Each chapter is paired with a different aspect of the emerging sciences, including perspectives from the study of embodied cognition, nonlinear dynamics, self-organizing systems, social networks, and situated and distributed learning. "Sync or Swarm" looks through the lens of contemporary science to illuminate the process and practice of improvising music and explores the ability of improvisation to offer a visceral engagement with these emerging scientific notions, ultimately offering us new ways of engaging with and shaping the discourse that surrounds music in general. The book comes with a 74-minute CD featuring performances by Evan Parker, the Sam Rivers Trio, George Lewis, and the author's own improvising collective, "Surrealestate".