Lady Gaga and Bradley Cooper's "Shallow" makes for an anomaly at the top of the Billboard Hot 100 in 2019 for a number of reasons. It's an unusual No. 1 as a pop-rock ballad with country DNA, as a duet between singer-songwriters, as a live-recorded performance, as a song lacking in conventional verse-chorus structure. Hell, it's even somewhat unusual as a Lady Gaga No. 1, since despite remaining one of the pop world's most successful stars, she hadn't previously topped the Hot 100 since "Born This Way" in 2011. But the most interesting thing about the "Shallow" triumph might be that it marks the return of a kind of chart-topper we don't see so often these days: The pop culture moment No. 1. In other words, a song that doesn't necessarily make sense as a contemprary No. 1 strictly in musical terms, but which can be explained through cultural context and the extra-musical factors that have supported it. READ MORE Lady Gaga & Bradley Cooper's 'Shallow' Surges to No. 1 on Billboard Hot 100, Fueled by Oscars Gains Such No. 1s have popped up all throughout the history of the Hot 100, perhaps experiencing their greatest renaissance in the '80s, when explosive instrumental themes to Chariots of Fire and Miami Vice made it to No. 1, along with long-simmering slow jams that experienced chart bumps thanks to their uses on hit shows like General Hospital (James Ingram and Patti Austin's "Baby Come to Me") and Family Ties (Billy Vera and the Beaters' "At This Moment"). The '90s film soundtrack boom also resulted in a number of unconventional chart-toppers in the next decade, like unsigned alt-rock act Lisa Loeb & Nine Stories' debut single "Stay (I Missed You)" (Reality Bites) and U.K. singer-songwriter Seal's power ballad "Kiss From a Rose" (Batman Forever). Meanwhile, the two longest-running No. 1s of 1997 -- Puff Daddy's "I'll Be Missing You" (featuring Faith Evans and 112) and Elton John's "Candle in the Wind 1997" / "Something About the Way You Look Tonight" -- were both powered by public grieving, over the then-recent deaths of The Notorious B.I.G. and Princess Diana, respectively.

In the '00s, following Christina Aguilera, Lil Kim, Mya and P!nk's Moulin Rouge-inspired "Lady Marmalade" reboot, the soundtrack-slingshot hits largely dried up, but a new form of pop culture moment No. 1 was introduced as a Hot 100 perennial: The American Idol single. Kelly Clarkson, Clay Aiken, Fantasia Barrino, Carrie Underwood and Taylor Hicks were all able to top the chart with their post-Idol debut singles, following their rise to stardom on the reality TV competition. But as the show started to wane in cultural impact, Idol alums stopped reaching pole position, and by the '10s, the most relevant form of the pop culture moment No. 1 came via the viral video -- which took advantage of then-new Hot 100 calculations that accounted for streaming services like YouTube, and propelled a song as unusual as Baauer's riotous EDM instrumental "Harlem Shake" to the summit. READ MORE Baauer's 'Harlem Shake' Debuts Atop Revamped Hot 100 But in 2019, we don't see any of those types of No. 1s very often. The last No. 1 that could be said to owe its chart-topping success mostly to extra-musical factors would arguably be Rae Sremmurd's 2016 smash "Black Beatles," which spiked on the Hot 100 months into its run as a single after the spread of the "Mannequin Challenge" meme propelling it to viral fame. (Drake's "In My Feelings" also benefitted from such a challenge, but as a highly streamed highlight from the new album by 2018's most accomplished Hot 100 hitmaker, it's not unreasonable to assume it would've found similar success even without it.) No. 1s from hit movies still pop up occasionally, but while Wiz Khalifa and Charlie Puth's "See You Again" -- an elegy aided by its emotional usage in Furious 7 following the death of franchise anchor Paul Walker -- is arguable as a 2015 pop culture moment No. 1, few would argue that the use of Justin Timberlake's "Can't Stop the Feeling!" in 2016's Trolls as a primary reason behind its chart-topping success. (We should allow a mention here as well for XXXTENTACION's "Sad!," a top 10 hit upon its initial release that surged to No. 1 following the artist's death last June.) But even compared to these other recent examples, "Shallow" is somewhat refreshingly pure, as an example of a song that simply wouldn't even exist without its parent movie. Specifically written for A Star Is Born as a kind of love theme between the main characters of Ally and Jackson Maine (played by Gaga and Cooper, respectively), "Shallow" is absolutely inextricable from Star, and it's unsurprising that its chart success has correllated almost directly with public excitement over the film. It debuted on the Hot 100 at No. 28 on the chart dated Oct. 13, the week after both Star's Friday release and the single's first full week of tracking, then jumped to No. 5 the next week following both the movie's first full week in theaters and the Billboard 200-topping soundtrack's first full week of availability.

The song descended the list from there -- although it remained in the top 40 for all but two weeks -- and, as excitement over the movie's Oscar chances built, it re-entered the chart's top 20 in February. And now, the song jumps to No. 1 in its 22nd week, following its win for best original song at the 2019 Oscars on Feb. 24, as well as a well-received (and much-streamed) live performance of the ballad by Cooper and Gaga at the ceremonies. Why is it important to have these kinds of pop culture moment No. 1s? Well for one thing, it offers much-appreciated variety at the top of the charts -- after a succession of up-tempo, streaming-friendly hip-hop songs and mid-tempo, radio-friendly pop&B hybrids, it's fun to have an old-fashioned pop-rock power ballad at No. 1 for the first time in ages. It also adds to a chart's feeling of really defining its moment in time: The memories of A Star Is Born at the Oscars will remain such a vivid part of the cultural memory of early 2019 that it feels only right that the No. 1 song in the country should reflect that. And perhaps most importantly, a No. 1 like "Shallow" gets the different core institutions of our popular culture -- movie theaters, radio, TV, social media -- in conversation with one another, enriching all of them in the process and allowing the culture to grow communally.