Speed of Sounds

I've notice that if Bob Marley's Buffalo Soldier comes on the radio, my speed drops by about 10 MPH before I realise I'm slowing down. Contrariwise listening to something really stirring and uptempo while driving, can add a few MPH to the speedometer. Apparently the same is true of funny stuff. If I get nicked, I'm blaming Brad Guigar and Dave Kellett.