As noted by Gingras et al (2015), emotional stimulation has been known to lead to pupil dilation and contraction. For dilation of the pupils to occur during the listening of music, the special senses must work in conjunction with the autonomic nervous system (ANS). In addition, for this study to be physiological fact, the special senses and the ANS must also work collectively with the peripheral nervous system (PNS) and central nervous systems (CNS).
Gringas, B., Marin, M., Puig-Waldmuller, E., & Fitch, W. (2015). The eye is listening: Music-induced arousal and individual differences predict pupillary responses. Frontiers Human Neuroscience, 9:619. doi: 10.3389/fnhum.2015.00619