Robin Thicke, Miley Cyrus

Robin Thicke and Miley Cyrus perform "Blurred Lines" at the MTV Video Music Awards in August. (Charles Sykes / Invision/Associated Press)

The record-industry score-keepers at Nielsen SoundScan recently confirmed something many music fans had probably already assumed: Robin Thicke's "Blurred Lines" — the cheeky disco-funk jam with the controversial, nudity-enhanced video — was the biggest-selling single of 2013, with 6.5 million copies sold.

The tune, nominated for record of the year at this month's Grammy Awards, spent 12 straight weeks atop Billboard's Hot 100, longer than any other song last year; that video, meanwhile, has racked up nearly 300 million views on YouTube.

However singular its domination, though, "Blurred Lines" was just one of a number of hits that reflected the return of raunch to pop music after several years in which propriety was a more dependable pose.

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In 2012, you couldn't turn on the radio without hearing Carly Rae Jepsen's squeaky-clean "Call Me Maybe" or "We Are Young" by the cuddly New York trio Fun.

Adele topped album sales that year and the year prior with her old-fashioned "21." And let's not forget — or maybe let's do — the self-consciously virtuous folk-rock revival that made mainstream stars of Mumford & Sons and the Lumineers.

By comparison, 2013 came in like a wrecking ball, to quote the year's most important vulgarian, Miley Cyrus, who set off a national debate about the boundaries of taste with her thrillingly lewd appearance alongside Thicke (and a giant foam finger) on the MTV Video Music Awards.

Pop always circles back to sex; it's low-hanging fruit ripe for the picking when innovation runs short, the economy tanks or a generation of kiddie-culture stars come of age.

But for listeners who count on artists to push limits, last year's wave of obscenity felt like a course correction after the conservatism of the early 2010s.

Cyrus pushed plenty. In wake of the VMAs, she extended the naughty streak with the clip for her chart-topping power ballad "Wrecking Ball" — it depicts a naked Cyrus astride just such an implement of destruction — and her album "Bangerz," on which the former Disney Channel star raps slyly about replacing a man with a battery pack.

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For Cyrus, 21, the twerking and tongue-wagging served as a rupture with her tween-idol past. Ditto Justin Bieber, who spent much of the year sketching a map of grown-up misbehavior, with unsavory incidents involving a mop bucket, a Brazilian brothel and a woman reported to be a porn star.

Yet as unified as they seemed in their determination to titillate, Miley and her peers each had their own agendas.

With "Blurred Lines" (and other off-color songs from Thicke's album of the same name), the 36-year-old's goal was the exact opposite of Cyrus'. He was using sex to age himself down and shake off the harmless adult-contemporary vibe he'd accrued thanks to his ultra-sensitive 2007 hit "Lost Without U."

You got the same feeling from Bruno Mars' "Gorilla" and its video, which starred Freida Pinto as a tequila-pouring pole dancer. Here was the kindly balladeer of "Just the Way You Are" in a racy rebranding effort.

More pointed bawdiness came from Kanye West, whose album "Yeezus" felt at times like an explosion of psycho-sexual politics, and Lady Gaga, who for her song "Do What U Want" enlisted R. Kelly for a little bump 'n' grind at the intersection of desire and celebrity.

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Kelly lent his imprimatur to several other stars in 2013, including Bieber (in the steamy "PYD") and Mars (in an even more lascivious remix of "Gorilla"). The veteran R&B star put out his own album too, "Black Panties," which after a string of decorous retro-soul discs heralded his re-embrace of the kind of outsized bedroom boast with which he'd made his name.

"Tonight," he sang, "you're lying with a sex genius."

And then, perhaps boldest of all, there was Beyoncé, who shocked the world in December first by releasing a self-titled album on iTunes with no advance warning, then by peppering the record with far more sex talk — much of it unprintable here — than she'd previously given us reason to expect.