The sound of silence. Not the Simon & Garfunkel song, but literally nothing. There's no music permitted in the office I work in. At my previous location within the same company, the plant manager (who is the plant manager at my current location as well) walked into the office and heard one of my former associates playing music on his computer while he worked. He told me the boss said "turn that off, this is not the whore house".
On the ride into work though, I was listening to Duff McKagan's Loaded "Wasted Heart" EP.