I'm not sure if I should answer seriously or act as the straight man for a stand-up routine. If I were to reply honestly, I'd say it's like math in that you have to have a grasp of how individual constants and variables (notes, lyrics, beats, etc) mesh together to fit the equation (the song). Sure, throwing random numbers together will sometimes create accidental equations that people will take as reality despite the flaws in the work (Black Eyed Peas, Bieber, and so on), but true mathematical solutions require knowing what you're doing, as opposed to simply lucking into an answer. Which pretty much means I'm doomed as a musician because I'm crap at Algebra.