Interesting point you bring up. Let me share with you a comment that a visiting teacher said to me about my class. She visited my class hoping to place a student in a suitable class because she is relocating out of state. I teach several different styles of yoga: Yin/Yang, Power and a mixed level class. She came to my mixed level class. I play music in all my classes, but not pop music. I play chants, and music that is appropriate for yoga. I begin with centering and meditation, gentle warm ups, a nice flow, pranayama and shavasana. Interestingly, after class she said that she is more familiar with vinyasa flow than the “traditional style” class I had just taught. I found this comment very interesting coming from a teacher, wondering how she sets up her vinyasa class if she thinks of mine as more traditional. Now I can think of ?'s I should have asked this new teacher like, "don’t you teach meditation or pranayama? What kind of music do you use? etc. etc. Vinyasa flow is just linking the poses with the breath. So I thought to myself, “Is this not what I had just done?” Vinyasa flow can be more fast paced or gentle. There is great flexibility here.
So I guess my point is it is all a matter of perception. Vinyasa flow can be relaxing and while my classes are a good workout, they are very relaxing and balancing. I’m sorry you have had such a bad experience in Michigan. But believe me when I tell you, vinyasa flow can be quite wonderful and calming. Much depends on the teacher and what the yoga community in your area wants. Many teachers brand their own yoga style, again because of what the community wants.
Answering your ? about trend? Yes I do see a trend toward more cardio and hip music and away from the traditions. I think this is very sad indeed.