"It was the first of its kind."

Billboard is celebrating the 2010s with essays on the 100 songs that we feel most define the decade that was -- the songs that both shaped and reflected the music and culture of the period -- with help telling their stories from some of the artists, behind-the-scenes collaborators and industry insiders involved.

Regularly, listeners erroneously describe K-pop as a “genre” of music. But unlike Europop, the geographic notation of “K-pop” doesn’t immediately bring a single sonic style to mind. Instead, it evokes the idea of pristinely crafted pop perfection that blends a wide range of musical styles.

And though many, many songs coming out of the South Korean pop scene have played with tonal shifts and BPM switcheroos, few have done so with such aplomb as Girls’ Generation’s 2013 hit “I Got a Boy” -- which is often compared to Queen’s tone-hopping epic “Bohemian Rhapsody” due to its pristinely chaotic approach to jumping between musical elements.

A medley of upbeat components blended together with a sense of frenzied vibrancy, “I Got a Boy” was imagined by Korean entertainment label as if it were pretty much a showtune, says songwriter Sarah Lundbäck. “They were so smart. ‘[People] get bored, you need to keep the interest up.’ They said they really wanted to make the song into a musical feel, in the storyline. Because they really wanted the song to be about a girl that meets a boy and all her friends are telling her, like, ‘You’re an idiot. What can you see in this boy? He’s not good for you,’ and she’s like ‘Well, I got a boy.’”

The result was a girlish discourse about dating wrapped in everything from pump-up chants to panicked raps to enraged pop-rock-fueled vocal belts. “In my head, it was like, ‘Okay, we can do something crazy,’” reflects Lundbäck, pointing to how the song goes through nine distinct tonal shifts. “And it really felt like it was crazy, and that was fun. It’s so not conventional.”

The track, which started out as a songcamp brainchild of Lundbäck, Will Simms, and Anne Judith Wik, nearly ended up with Missy Elliott -- but once SM Entertainment got its hands on it, the K-pop company’s producing division says via a joint statement that the A&R team, “came up with various ideas by editing the song day and night.”

A major success, the song debuted at No. 1 on South Korea’s Gaon singles chart. The music video for “I Got a Boy,” which won video of the year at the first, and only one of two, YouTube Music Video Awards, was a colorful explosion of visual confectionary that enhanced the audio elements, and helped spread it across the globe as a viral hit.

Tiffany Young, a Girls’ Generation member who is now pursuing her solo career based out of LA, says the song’s eclecticism came out of the act’s need to show a new side to themselves. It was in part inspired by two female managers they worked with at the time who empowered them to put forth a style of music that suited them more as they aged, something that felt different and bolder. “We had discussed that we wanted to do something more challenging,” she says. “This felt like it was it, because I had never heard anything like it yet. The song is a song that keeps giving.”

Overall, “I Got a Boy” showed the world what a little ingenuity could do without being hampered not only by genre limitations, but also by perceptions of an individual act’s artistic identity. As we approach the end of the decade, genre-blending is no longer only commonplace in K-pop but increasingly more and more musicians refuse to color in the lines resulting in more dynamic music than ever before. “I Got a Boy,” the epitome of this, set the standard for the industry moving forward, and upped the bar for 21st century musical experimentalism. “I think it was the first of its kind,” says Young.