This chapter introduces psychoneuroimmunology: a field that explores how our biological processes are influenced by our mental events and processes, and how these same biological processes also have the ability to modulate the function of the mind. It considers how our emotions affect biological markers including hormones and inflammatory immune proteins, and explores results from recent research into the interaction between music, emotions and biological markers. Analyzing the effect of music on neuropeptides, hormones and cells and proteins of the immune system can truly inform our understanding of music and emotions.