In the traditional Mysore Ashtanga class the practice is done with no music as the practitioner is encouraged to turn the attention inward and listen to his or her own breathing. To be honest, when I started Mysore Ashtanga, it felt weird and also funny because all you can hear is your fellow yogis inhaling and exhaling loudly.
Over the time, however, not only I got used to it, but I also realized that it helped me improve my breathing. Now I am a big fan of my silent Mysore mornings. :)
At the same time, I do not oppose having music in Vinyasa classes. On the contrary, the right music can really set the tone of a class and can serve as an additional way for the teacher to communicate with students.
In my opinion, sometimes yoga teachers overdo it with preaching yoga philosophy and spirituality. This might even be perceived as pretentious, if not cheesy. I would much rather communicate my message non-verbally: through my flow - and through my choice of music.