During my first yoga class she played new agey music, and I enjoyed it a lot. It was peaceful and relaxing while we did our yoga movements.
During this second one she had music with words, like Michael Jackson songs. Not only did they distract me, because I started listening to the words rather than focusing on my yoga poses, but also sometimes it made it hard to hear what she was saying because her instructions would get run over by the lyrics.
So I think I'd rather have wordless music for yoga.