  In this chapter, we focus on two main categories of visual interaction: body
gestures and gaze direction. Our focus on body gestures is motivated by
research showing that gesture patterns often change during joint action tasks
to become more predictable (van der Wel et al., 2016). Moreover, coordination
sometimes emerges between musicians at the level of body sway (Chang et al.,
2017). Our focus on gaze direction was motivated by the fact that gaze can
serve simultaneously as a means of obtaining information about the world and as
a means of communicating one's own attention and intent.
