In Mac Miller’s new single, “Of the Soul,” released Thursday, the young’n introduces some new and mature (pronounced “ma –toor”) aspects of his art. Namely, he has glasses. And raps to a slower, more sensuous R&B tempo. And has an actual sound stage instead of a playground (because nothing screams adult like modern art, rather than a blue slide). Anyway, I surprisingly like this heartfelt ditty. Does it have the depth of “Nikes on my Feet,” or the political heft of “Donald Trump”? Maybe not. But at least Mr. Miller has facial hair in this one, and that, my friend, makes him a man.