Pharrell Williams

Pharrell Williams performs on stage at Google presents YouTube Brandcast event at The Theater at Madison Square Garden on April 30, 2014 in New York City.

Stephen Lovekin/FilmMagic

A look at the biggest chart headlines, from Pharrell Williams, Michael Jackson, Iggy Azalea and more, from the first half of 2014

Fourteen chart headlines from the first half of 2014:

Katy Perry's "Dark Horse" (featuring Juicy J) wins the race to No. 1 on the Billboard Hot 100 (Feb. 8). The song, infused with trap elements, marking a slight departure from her standard pure-pop fare, is her ninth career leader. "This No. 1 is the most unexpected one I've ever had," Perry told Billboard. "'Dark Horse' has been a dark horse of a song, since the KatyCats voted to release it early on iTunes, before [parent album] 'PRISM' even came out. I'm so thrilled and grateful to have these moments."

Pharrell Williams' 10-week Hot 100 leader "Happy" (which began its reign on March 8) becomes the first song to crown as many as six singular-format Billboard airplay charts, achieving the feat by rising 3-1 on Adult Contemporary. Its other rules: on Pop Songs, Adult Pop Songs, Rhythmic Songs, Mainstream R&B/Hip-Hop Airplay and Adult R&B Songs. Four prior smashes each led five distinct-format airplay charts: Robin Thicke's "Blurred Lines," featuring Williams and T.I. (2013); Gotye's "Somebody That I Used to Know," featuring Kimbra (2012-13); Green Day's "Boulevard of Broken Dreams" (2004-05); and Boyz II Men's "I'll Make Love to You" (1994-95).

One Direction scores its first No. 1 on a Billboard radio airplay chart, as "Story of My Life" rises 2-1 on Adult Pop Songs (March 22). The group had reached No. 5 on the survey with "What Makes You Beautiful" in 2012, but hadn't returned to the top 10 of an airplay tally until "Story." Sue O'Neil, program director of Adult Pop Songs panelist WTSS Buffalo, N.Y., credited the organic lean of "Story" for its success. "It's a new, more contemporary sound for One Direction. You find yourself singing and liking the song whether or not you normally like the boy-band sound, or even One Direction. It's a great song."

John Legend collects his first Hot 100 No. 1, almost 10 years to the week of his first appearance on the chart (May 17). He ended the longest wait for an act's first No. 1 (from a first chart entry) since Snoop Dogg took 10 years and 10 months before finally leading with "Drop it Like It's Hot," featuring Williams, in 2004. And, while no Hot 100 No. 1s featured only vocals and piano for the chart's first 53 years, three have done so since: Adele's "Someone Like You" (2011), Bruno Mars' "When I Was Your Man" (2013) and "All." ("All was also powered by its uptempo Tiesto remix, which many pop radio stations have favored.)

Disney's soundtrack to "Frozen" logs its 13th (and last to date) week at No. 1 on the Billboard 200, extending its reign as the longest-running No. 1 soundtrack by an animated film (May 17); it surpassed "The Lion King" (10 weeks, 1994-95). "Frozen," which produced the No. 5 – and Best Original Song Oscar-winning – Hot 100 hit "Let It Go" by Idina Menzel, is now one of only 39 albums in the 58-year history of the Billboard 200 to have spent at least 13 weeks at No. 1.

Imagine Dragons' "Radioactive" drops off the Hot 100 after a record-setting 87 weeks on the survey (May 17). "It's unbelievable," Imagine Dragons lead singer Dan Reynolds told Billboard when the track set the mark, previously held by Jason Mraz's "I'm Yours" (76 weeks, 2008-09) for the most weeks on the chart. "There are few things more satisfying as an artist than seeing your music have longevity. But, we could never have expected to see one of our songs have legs like this. "People seem to be connecting to it in personal ways, which is exactly what we hoped for. We've been out on the road and focused on touring for a long time. Somewhere along the way, we started to realize the song was taking on a life of its own."

Hillsong United rewrites the record for the longest reign on Billboard's airplay/sales/streaming-based Hot Christian Songs chart, as "Oceans (Where Feet May Fail)" tallies a 24th week at No. 1 (May 17). The song passes the 23-week rule of MercyMe's "Word of God Speak," which began its command on Aug. 16, 2003 (when the chart, which had launched two months earlier, was solely airplay-based). "What people relate to is that it's a very honest song," Hillsong United leader/principal songwriter Joel Houston told Billboard. "It's about trust and taking a step into the unknown."

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