My wife and I alternate in our opinions on music or not during practice. Silence allows the breath to become the soundtrack and strips away another confounding variable – sound. Yet, no practice is completely silent, so any sound does become incorporated in the practice. Silence is natural.
Music on the other hand can shoe-horn the soul into a gentle place and allow it to further open up. Music can allow the heart to enter sacred places and allow the mind to let go. Music is somewhat magical.
There is of course no right answer as context is everything. For example, what type of yoga is being practiced? Is the practitioner new to yoga and music makes the transition to simply “being” less threatening.
And then there is the music itself. Bad music can distract us and put us in the mind, away from breath. So if it is music, then it must be supportive.