The problem of cross-genre covers.

Jay-Z knows how to handle himself in a rap feud; he's triumphed in battles with some of hip-hop's sharpest tongues. But this spring, he was presented with an unfamiliar sort of antagonist. In an interview, Oasis' Noel Gallagher scoffed at the news that the Brooklyn MC had been invited to headline in Glastonbury, a longstanding U.K. rock festival: "Glastonbury has a history of guitar music," he said. "I'm not having Jay-Z at Glastonbury. It's wrong." At first, Jay-Z rebutted with a rather polite sound bite: "We don't play guitars, Noel, but hip-hop has put in its work like any other form of music." But earlier this month, at the festival itself, his response took on an unlikelier, funnier, and more devastating form. He performed a cover.

The song was "Wonderwall," the old Oasis hit, and it opened Jay-Z's performance. He strolled out pretending to strum an electric guitar as the original played over the speakers. Wearing a delighted grin, he missed big chunks of the lyrics, flubbed many of the rest, and delivered everything in a tone-deaf sneer. It was a mess, but that was the point: Jay-Z wanted the guitar to look like a big, goofy prop (in Gallagher's formulation, after all, guitars aren't instruments so much as membership cards); he wanted to mistreat the melody, not coddle it; and he couldn't be bothered to remember lyrics that, when you think about it, sound sort of flubbed to begin with. By butchering the cover, Jay-Z weaponized it.

Jay-Z's sarcastic "Wonderwall" illustrates a deeper truth about cross-genre covers in general (indie boys covering teen starlets, lounge lizards covering metalheads, bookish singer-songwriters covering R&B Casanovas, etc.): These songs often contain a thorny tangle of value judgments, power dynamics, and aesthetic agendas. Unlike polyglot MP3 blogs, mash-ups, and the iPod's shuffle function—all of which enable exhilarating collisions and unlikely harmonies between different sounds, reflecting a digital-era erosion of musical boundaries—cross-genre covers don't necessarily reflect anything so utopian. The seemingly neutral act of singing someone else's song can function as an argument, a slap, a grenade toss.

"Wonderwall," as it turns out, has been butchered before. Pavement recorded a similarly abusive version—full of forgotten words, dropped notes, and disdainful chuckles—during a late-'90s BBC appearance. This was a brutal piss-take and an act of snobbery through and through: scruffy grad-school types swiping at rock-star roosters, draining the song of bravado and leaving it shriveled on the studio floor. Snobbery animates many cross-genre covers. Alanis Morrissette's best song in years was her 2007 re-envisioning of the Black Eyed Peas' giddily inane "My Humps."

But snobbery isn't always so likeable. A band as ridiculous as Oasis can sustain—deserves, even—all sorts of mockery. By contrast, there can be something smug and unseemly about indie-rock jabs at big-money pop. One wonders why Ben Gibbard bothered with his live cover of Avril Lavigne's "Complicated" if he was going to snicker so much throughout it. "No, no, it's a serious song!" he shouts in false protest when the crowd snickers, too. With his band Death Cab for Cutie, Gibbard spares no syllable in his quest to detail even the most trivial emotional state; his goal here seems to be to fault Lavigne for failing to bring the same nuance to her pubescent social drama. "The thing about that song I love is, I don't really understand what's so complicated!" he says to rapturous laughter when the cover is done. "It seems pretty cut-and-dry!" There's something genuinely admiring in parts of his performance, but it's smothered by a greasy layer of condescension.