You've heard that song before. Why does it make you feel something when it's in 'Barbie?'

In June 2022, singer Kate Bush told BBC Radio 4 that she hadn’t listened to her 1985 song “Running Up That Hill” for “a really long time.” She hadn’t even performed it live since 2014. Then, 37 years later, it suddenly shot up the charts to become her first-ever U.S. Top 10 hit.

“Running Up That Hill” was Bush’s lead single from her fifth album and peaked at No. 30 on the Billboard Hot 100 when it was first released. It had decent commercial success but was not even close to getting the plays it got after it was featured in an episode of Netflix’s Stranger Things. It was everywhere — even the soundtrack to a TikTok trend, one of the coveted ways to have a song go viral — and hit 1 billion streams on Spotify, making it the first solo recording by a female artist from the 1980s to achieve the benchmark.

Since then, several songs from the late '90s and early 2000s have found new life after being featured on movie soundtracks.

Barbie reintroduced “Push” by Matchbox Twenty (director Greta Gerwig specifically chose the song); Saltburn boosted Sophie Ellis-Bextor’s 2001 disco hit “Murder on the Dancefloor,” which didn’t even hit the Billboard Hot 100 Chart when it was first released (like Gerwig, director Emerald Fennell, who grew up in London, also chose the song for the final scene of the movie). Will Gluck, the director of rom-com Anyone But You, contacted Natasha Bedingfield directly to use “Unwritten” in the soundtrack, causing the song to chart again in the U.K. for the first time in 19 years.

Using older songs in movie soundtracks isn’t new. Musicologist Nate Sloan, who co-hosts the podcast Switched on Pop, told Yahoo Entertainment that it has been a well-established practice since at least the 1960s. The difference is that more than ever listeners and viewers crave nostalgia.

“Pop music itself has ‘gone retro’ with interpolations of older songs becoming commonplace on the Top 40,” Sloan said, referring to Ariana Grande’s recent single “Yes, And?” referencing Madonna’s 1990 hit “Vogue.”

“As a result, listeners and viewers are more primed than ever for nostalgic content,” he explained. “Music and film have always been closely tied.”

Joe Bennett, a forensic musicologist and professor at Berklee College of Music in Boston, agreed, crediting Wayne’s World for helping to boost the popularity of arguably Queen’s most enduring song.

“Queen’s ‘Bohemian Rhapsody’ achieved a higher chart position in 1992 than it did on its original release,” Bennett explained, attributing the revival to it being featured on the Wayne’s World soundtrack. “A middle-aged person’s over-played FM radio staple might be a Gen Z-er’s undiscovered gem.”

Sloan told Yahoo Entertainment that it’s nostalgia that connects all of these soundtrack songs and makes them resurge in popularity decades later.

“While Kate Bush and Matchbox Twenty could not be more different sonically, what connects them and makes them both excellent fodder for soundtracks is the way each of their songs is tied to a certain moment in time,” he said.

The certain moments in time, or nostalgia, that these songs produce are the epitome of a successful soundtrack. The purpose of soundtracks is to foster an emotional connection with the audience — when done correctly. Otherwise, it can be distracting.

Sloan also points to TikTok as a driving force behind these songs reaching audiences beyond those who saw the movies.

“TikTok, far from ‘killing’ the music industry, has become a key part of the business model,” he said. “It serves as an additional platform for successful artists.”

Bennett explained that the current music streaming model makes it easier than ever for young people to discover old music: They don’t have to listen to the radio or buy full albums. He also has noticed some TikTok influences — not necessarily good or bad — in current pop music: Songs are shorter and more artists are starting with the chorus and eliminating the traditional second verse.

But, ultimately, Bennett attributes the revival of these songs to be a testament to the song more than anything else.

“I think the phenomenon is largely down to the quality of the music itself,” he said. “Social media is literally a connector; I suggest it is simply a conduit to connecting [a] great back catalog to an audience who wouldn’t otherwise connect with it.”