Charlie Harding is the co-host of Switched On Pop, the podcast that breaks down how popular music works.

This is the year of the "pop-drop," the post-chorus musical interlude that blends techniques from electronic dance music to hip-hop, and it's taken the chorus' place in pop music. The pop-drop is the new climax of the song, right where we would expect to hear the chorus, and it is absolutely everywhere.

It's set up by what's known as the "pre-chorus," which typically cues a sing-along refrain. Then where we expect the chorus, we get yet another section of build, a kind of pseudo-chorus that further heightens expectations. Finally, the pop-drop lands. The singer literally drops out, replaced by synthesizers and chopped-up, distorted vocal samples that vaguely reference the earlier lyrics. There is no need to sing along. Paired with a syncopated beat, the pop-drop invites the listener to just feel the music in a way that's unexpected, revelatory and just plain fun.

In 2016, about two out of every 10 songs on the Billboard Hot 100 contained a pop-drop, but for the moment, The Chainsmokers are the undeniable pop-drop champions of 2016. "Roses," "Don't Let Me Down," "All We Know" and their 12-week Hot 100 No. 1 "Closer" all put the pop-drop front and center, with the calculated deployment of a NASA launch: A 10-count intro, followed by a perfunctory 20 seconds of narration. Then the minute or so of pre-chorus and pseudo-chorus light up the engines. All set up, right around 1:15-1:25, the pop-drop takes off. And it will burst out two or three times before the song comes crashing back down into silence.

Let's take a closer look at "Closer" to see how the pop-drop works:

[PRE-CHORUS]

I know it breaks your heart

Moved to the city in a broke down car…

[CHORUS]

So baby pull me closer in the backseat of your Rover

That I know you can't afford

Bite that tattoo on your shoulder

Pull the sheets right off the corner

Of the mattress that you stole

From your roommate back in Boulder

We ain't ever getting older

[POP DROP!]

But The Chainsmokers are not just borrowing from themselves; they're adapting a sound that grew out of '70s rock and developed in the 2010s through the EDM festival anthem: simply called "the drop." It is the moment of instrumental build when the bass and rhythm hit hardest. It's why arenas full of people suddenly start jumping up and down.

The pop-drop descends from this lineage. But because instrumental music fares poorly on the charts ("The Harlem Shake" aside), producers looking to cross over into pop needed a vocal star to sneak the sound into the mainstream. Producers like Skrillex, Diplo and DJ Snake found their perfect candidate in Justin Bieber. To reclaim and sustain his status as a chart-topper when he was at his musical and personal low point, grown-up Bieber desperately needed a new image and sound.

Bieber's admittedly smooth, listenable tenor could unite the power climax of EDM with familiar pop song structures. Skrillex and Diplo's collaboration as Jack Ü premiered this new sound with "Where Are Ü Now." On the track, Bieber leads us through a conventional verse, over which Skrillex gradually re-pitches, distorts and augments Bieber's voice until it's completely transformed. When the pop-drop lands, we're left with an insane dolphin-like squeal, pulled from the essence of Bieber's voice in a call and response, that echoes past vocal phrases, and drives home the song's title: "Where are you now that I need you?"

On first listen, it's a sonically bizarre song. Seemingly unfit for pop radio, Skrillex and Diplo reference well-established techniques from hip-hop. DJ Snake used similar vocal samples on his collaboration with Lil Jon, "Turn Down for What." The crossover dance/hip-hop track reimagined the squeaky, haunting "chipmunk soul" sound of RZA, Kanye West and Jay Z that was ubiquitous in the '00s. The re-pitched samples of old soul singers on West's "School Spirit" reference early hip-hop when DJs sped up their turntables in search of the right tempo on the break, often leaving altered voices in the background like on the Cold Crush Brothers' "Rocket in the Pocket." The deep-rooted custom of sampling and re-pitching voices made it palatable to do the same in EDM. But in combination, chipmunk soul delivered in an EDM drop ushered in a novel sound.

The collaged approach to "Where Are Ü Now" started a trend. The producers refined this sound through "What Do You Mean?" and "Sorry," both an extension of the original. Together, all three songs weave together a continuous narrative about a broken relationship: "Ahhh where did you go?" dovetails into "What did you mean by that?" and is answered by "Oops I'm sorry I screwed up." A star was reborn, and he put a spotlight on a novel sound that skyrocketed EDM producers to the top of the charts.

The pop-drop's chart success has led to imitations across genres. New artists like Kiiara, FRENSHIP and Charlie Puth have all used this technique, seeking to capture the pop-drop audience. And like Bieber, established artists aspiring to stay relevant (Coldplay, Rihanna, Maroon 5) have embraced this new vocal distortion. The sound's meteoric rise has gone from genuine crossover innovation to overused musical fad.

The pop-drop is having its moment. It has elevated expectations beyond the chorus, paving the way for new mainstream song structures. And we might as well embrace it while it lasts because it may just be the sound of 2016. If pop history teaches us anything, before we know it, this sound will fade into the background, taking its place with the rest of pop nostalgia. Let's hope Bieber's producers have something else up their designer sleeves.

Listen to the complete discussion of the pop-drop on Switched On Pop.

Examples of recent Hot 100 songs with pop-drops:

"Closer" - The Chainsmokers feat. Halsey

"Let Me Love You" - DJ Snake feat. Justin Bieber

"Don't Wanna Know" - Maroon 5

"Cold Water" - Major Lazer feat. Justin Bieber & MO

"Gold" – Kiiara

"Don't Let Me Down" - The Chainsmokers feat. Daya

"Starving" - Hailee Steinfeld & Grey feat. Zedd

"This Is What You Came For" - Calvin Harris feat. Rihanna

"Luv" - Tory Lanez

"In the Name of Love" - Martin Garrix & Bebe Rexha

"Hymn for the Weekend" (Seeb remix) - Coldplay

"My Way" - Calvin Harris

"We Don't Talk Anymore" - Charlie Puth feat. Selena Gomez

"All We Know" - The Chainsmokers feat. Phoebe Ryan

"Capsize" - FRENSHIP & Emily Warren

"Chantaje" - Shakira & Maluma

--Additional reporting by Shane Dutta