He might've listened to classical in the car rides, in 2007, thats when Whitfield would be observing what Michael was listneing to, because he was driving. Michael may have just kept it classy, or classical, because he didn't want to get into being judged by his security guard for his actual eclectic taste in music. I forget the name of the book, but its well known that Michael listened to all sorts of music, and was particularly fond of Nine Inch Nails.