You're not hearing classical music; you're hearing a few phrases from the first part of Carmina Burana, set to a piece of "music" that Carl Orff did not write. Now, the lyrics to all of Carmina Burana are based on various medieval poems and drinking songs, so anyone is, of course, free to use them for whatever monstrosity they want to throw together, but don't tell me that the piece of music in that video is "O Fortuna Imperatrix Mundi" by Carl Orff, because it's not. He didn't write that thing. This is no different from rewriting a work of literature because it's too complicated. I can't write down "We are the hollow men / the end", and say it's T.S. Eliot. It's not.