Makes sense, right? Whatever the verb here, it should be in the past tense, not present. And nothing makes "pretend" more plausible than "began" (well, nothing I can see in the lyrics.) But pretend it is, and quite clearly enunciated, as pop lyrics go.
Moments later, as I was shaking off my long-standing delusion, Block revealed that she too had mondegreened* the lyrics. "Are the leaves all down?" she asked Patchett, who lives in Nashville. "All the leaves are down," Patchett replied. But no: It's "All the leaves are brown," to go with the gray skies (though the image of bare branches is nice too).
Will mondegreen creation dwindle when we all get our music via earbuds rather than crackly radios? Or is the listening mind just too inventive to stop making its own kind of sense, given half a chance? I'm rooting for the mondegreens; like eggcorns, they're too entertaining to be sacrificed for mere accuracy.
*I see that this verb is out there, in active and passive forms. I'll vote for active, since mondegreening is something we do, not something the song does to us.