I'm guessing syncopation. I've never seen the tempo marking "Heavy head banging" before. lol.
Here's a recording on youtube you can play along with:
http://www.youtube.com/watch?v=Fv23uXqT8GQ
NOTE: The recording skips from measure 25 to measure 34.
It's a bad recording, but something to work with.
-Stephen (Piko)