Buddhist Death Metal

I have often wondered what that Buddhist monk in his saffron robes is listening to on his IPod when he is sitting in the airport departure lounge - Dharma? Chanting? - what?  I dont know that there is an acceptable protocol for asking.  Yesterday in the Taipei airport there was one siting there and he was tapping his feet and playing air drums on his knees in such a tempo that it could have been the hardest death-metal band he was listening to.  I am even more confused now.