Specific acoustic frequency bands in the environment elicit different emotional experiences, which are paralleled by adaptive physiological states. Each of these physiological states is functionally an adaptive state that influences affect
regulation, social engagement behaviors, and our ability to communicate. We experience these states with feelings of safety, danger, or ultimate demise (i.e., life threat). Physiological state is an implicit component of the subjective experience of listening to or producing music. Music changes not only our emotive state, but also elicits changes in
our physiology that parallel the feelings of anxiety, fear, panic, and pain. For example, while listening to certain melodies, we relax, slow our heart rate, and smile. However, while listening to other music, we may start to imagine danger and
visualize marching off to war or protecting our loved ones. The feelings of danger will change our facial expression and increase our heart rate.
As Oliver Sacks discussed in Musicophilia (Sacks, 2007), music appears to be part of the human experience, yet no brain area or circuit has been identified to explain or represent music. This chapter approaches this question differently and
asks a different question. Rather than seeking specificity in the neural regulation required to process and to express music, the chapter will discuss the convergence and similarity between the neural mechanisms required to process music and the neural mechanisms required to process features of social engagement behaviors and risk in the environment. This convergence between physiological state and music-related emotional experience is neurophysiologically determined and explained by the Polyvagal Theory (Porges, 1995, 1997, 1998, 2001, 2003, 2007). The Polyvagal Theory will be used as an organizing principle to explain how music, and especially music when expressed via music therapy, can recruit the neural mechanisms that integrate facial muscles and visceral state, which in turn promotes restorative affective states and prosocial behavior.