Standard (EADGBE)

  Now, every once in a while, there's a crack in my smile...etc.

the little dun...da-dun...da-dun-da-dun-da-dun part right before the chorus

is an Em, then slid up 1 fret. So the fret pattern is 2...3-2...3-2-3-2-3-2

Breakin' Up!