Actually, I would consider it a non-magical centering technique. Something along the lines of meditation. You get into a mind-set when listening to certain music. This, in turn, allows you to get into a very, very low level trance state where certain actions become easier and more natural-feeling. In this case, weeving in and out of traffic at high rates of speed would be enhanced by the high-speed, thrash rythmes. So I would just give an across the board -1TN, but no more than that.
Gabriel