“It’s the craziest thing I’ve ever seen in my life,” remarked Benny Blanco, who co-produced the hit track. Sia’s prowess as a songwriter is legendary in the industry.

The 48-year-old hitmaker penned Rihanna’s iconic song “Diamonds” in the time it took to wait for a cab, according to Blanco. During an appearance on SiriusXM’s The Howard Stern Show on May 14, Blanco, who witnessed the moment and co-produced the 2012 hit with Stargate, recalled the astonishing speed with which Sia composed.

“Sia writes a song in under five minutes,” Blanco, 36, told Stern. “It’s the craziest thing I’ve ever seen in my entire life.”

“She was waiting for a cab — this was before Uber — and they said it’s going to be 15 minutes,” Blanco recounted. “And she said, ‘Oh, well just load up another thing.’”

And with that brief interval, the now-iconic track was born. “Song, melody, lyrics, harmonies, everything all done before the cab comes,” Blanco marveled. “And she’s like, ‘Yeah, that’s pretty good.’”

Had Sia’s taxi arrived sooner, “Diamonds,” which became Rihanna’s 12th No. 1 hit on the Billboard Hot 100 and spent three weeks there, might never have been created.

Stern questioned why Sia, known for her vocal contributions to hits like “Chandelier” and “Cheap Thrills,” would give away a hit like “Diamonds” to another artist “like it’s a throwaway.” Blanco defended the decision, explaining, “You have to remember, a lot of people are songwriters. You never know how a song’s going to feel or how it’s going to hit you.”

He continued, “Rihanna is such a special artist that the second her voice touches something it’s like a firework. She has so much tone and personality.”

Reflecting on the song’s journey, Blanco shared his initial uncertainty about its potential. “When we first made the demo I was like, ‘This is cool. I don’t know.’ Cause we wanted to give the song, at the time, to Kanye or Eminem.”

Eminem eventually recorded a version of the song, though he didn’t inform Blanco until much later. However, Blanco’s perspective shifted when Rihanna took on the track. “But then once Rihanna sang it, I was like, ‘Oh my God, this is something,’” he recalled.

Blanco, who has produced for numerous artists including Ed Sheeran, Katy Perry, and Selena Gomez, also spoke about his personal life, hinting at marriage with Gomez. Meanwhile, Sia remains busy, currently executive producing an album for Paris Hilton. In a recent interview with Billboard, Hilton revealed, “No one really knows this, but I’m actually a very shy person, like painfully shy. But with [Sia], I just feel so comfortable so I really sang in ways that I never knew were possible.”

Throughout his conversation with Stern, Blanco offered a glimpse into the music industry’s creative process and the personalities behind its biggest hits.