... Dylan (is supposed to have?) said about Mark back in the day. I guess he was referring to Mark's vocals.
Listening to the recordings from the current tour, I can't help but notice that Mark has a much more aggressive vocal style, like a rough snarl at times. Influenced (again) by Dylan?
ADDED:
So what do YOU think is the reason for added burst of energy, zest, aggressiveness, mojo?