听力原文：W: Today's arts report betrays Dan Parker of the American Indian Dance Theater. Mr. Parker, I understand your troupe performs traditional music and dance from many different Native American cultures. Can you give us an idea of some of the dances you'll be doing in your performance tonight? M: Certainly. We'll be doing won-us-award dance. Originally it was a story telling device to recount battles. Another is the grass dance, performed by the plains Indians, where they actually flatten tall field grass to prepare it for a ceremony. W: Since your dancers are from different tribes, how can you be sure the dances are done correctly? M: Everything we do had been approved by the elders of our tribes. That's partly because we don't necessarily know each other's styles or dances. But it's also because it's hard to get complete agreement even within the same tribe about exactly how the dance should be done. W: Anyone who attends one of your performances will notice that your company goes to a lot of trouble to pro vide detailed explanation of the origin of the dances, the music, the costumes and so forth. Could you ex plain to our listeners why you do these? M: Good question. There are always concerns that traditional dances performed in a theater are nothing more than spectacle. Our explanations show that in our cultures, dance is ritual rather than entertainment. What is the main topic of the conversation?