Every singer has their own ritual in the recording studio. Kelly Clarkson drinks olive oil to coat her throat. Stevie Nicks prefers a tequila. John Legend goes for half a rotisserie chicken.
And what about Olivia Rodrigo - 2021's biggest break-out star? She simply asks her producer, Daniel Nigro, to film her singing.
At first, he couldn't understand it. "I'm a person who buckles under pressure," he explains. "You put me on camera and all of a sudden I get in my head and I can't perform.
"But with Olivia, it's the exact opposite. You'd say, 'OK, we're filming you, people are watching', and all of a sudden she gives the performance of a lifetime. It became a bit of a joke between us."
There's a logic to her approach. Rodrigo started out as an actress, first in the Disney series Bizaardvark, then in the hit streaming show High School Musical: The Musical: The Series. She's used to switching into performance mode when the red light goes on.
"Acting definitely comes into play for me when I'm recording," she admits. "I'm so into it, I will screw up my face and act out every word I'm singing.
"I think that makes the performance on the eventual record so much more impactful."
That's not to imply that Rodrigo's songs are anything less than authentic. Every note she sings is distilled from raw emotion.
You can hear it in Drivers License, her instant-classic debut single, which filleted the true story of Rodrigo passing her test, then driving past the house of the ex she had planned to celebrate with, to devastating effect.
Released in January, a few weeks before her 18th birthday, it broke Spotify's record for the most streams in a single day (excluding Christmas songs), then beat its own number the following day. In the UK, it topped the charts for nine weeks. In America, she became the first female artist to have a song debut at number one since Lauryn Hill in 1998.
The week after the single came out "is such a blur", she says. "There's a feature on Spotify where you can see how many people are listening to a song at any given moment, and I remember going, 'Oh my God, 60,000 people are listening to Drivers License, right now.' That was insane. I couldn't wrap my head around that number."
Some commentators attributed the success to the intrigue surrounding the lyrics: fans deduced it was written about Joshua Bassett, Rodrigo's co-star on the High School Musical series, and that her romantic rival, a "blonde girl" who's "so much older than me", might be another Disney star, Sabrina Carpenter.
But most listeners neither knew nor cared about those details. They simply resonated with the exquisite anguish in Rodrigo's delivery - something she'd always suspected was the secret ingredient.
"I personally always felt such a connection to that song," she says. "I would listen to it in my car alone if I was feeling sad because it perfectly captured how I was feeling, in a way that songs I'd written before didn't."
The fact that millions of others felt the same way, "reaffirmed this hypothesis I've had since I was a little kid, that vulnerability is always the most attractive thing in songwriting", she says.
Natural born performer
Rodrigo has been singing as long she can remember. Growing up in Temecula, California, she would belt out the choruses to No Doubt's Bathwater and the White Stripes' Seven Nation Army - songs she'd been introduced to by her mum, Sophia, a school teacher and alternative rock fan.
She started vocal lessons in kindergarten and by the age of eight was a talent-show regular. Her ability to inhabit a song was evident even then.
"I was so dramatic," she laughs. "There's videos on YouTube of me singing, and I'm so into it. I act everything out and I'm so performative. People always told my mom, 'You should put her in acting lessons.'"
Before long, the family was making 90-mile journeys to LA for auditions. In 2016, aged 12, Rodrigo was cast on the Disney Channel series Bizaardvark, starring as Paige Olvera, a teenager who posts funny songs and videos online.
She had to learn guitar for the role, a skill she carried over to High School Musical: The Musical: The Series, where she plays a student involved in a school production of the classic 2006 Disney musical.
When the show's creators discovered Rodrigo was a budding musician, they encouraged her to write for the series. One of her songs, a power ballad called All I Want, racked up millions of streams and became a minor chart hit.
But it was a different song that led to her extraordinary solo career. In January 2020, during a break in filming, she hunched over her guitar and wrote a lyric about watching her ex move on.
"Find someone great but don't find no-one better / I hope you're happy, but don't be happier."
She posted a clip to Instagram, where it caught the attention of Daniel Nigro, a writer and producer who's previously worked with Lewis Capaldi and Carly Rae Jepsen.
"It was a combination of the way she sang it, the intensity in her voice and the lyric," he recalls. "It just hit me and I was like, 'This is it.'"
He DM'd her instantly and they'd arranged to work together, before the pandemic brought everything to a shuddering halt.
Months later, amid strict safety protocols, they hunkered down at Nigro's home studio and started to bring her song sketches to life.
"Dan was one of the only people I worked with who told me, 'You can do better than that. That's not your best'," Rodrigo recalls. "And I was like, 'Oh wow, OK, this is how I'm going to get better as a songwriter.'"
Nigro stresses that there was very little room for improvement. The draft of Drivers License that Rodrigo brought to the studio, for example, was almost complete.
He helped arrange the chorus so it had "more of a sense of release"; and they wrote the spine-tingling middle 8 ("red light, stop signs") to set the scene for the final, devastating chorus. Otherwise, the song was essentially the same one you heard on the radio.
"She takes songwriting more seriously than anybody I've ever met," Nigro says. "Her attention to detail is just incredible. She'll rewrite and rewrite until she feels like every line makes total sense for what the song is trying to say."
'Crippled by comparisons'
Neither of them was prepared for the way the song took off - but that wild, overnight success also made Rodrigo reassess everything she'd written so far.
"I had an EP ready, like five or six songs. Then Drivers License came out and I was like, 'I'm just not super-proud of this'," she says.
"I knew that, after Drivers License, there'd be so many eyes on [me] that wouldn't have been there before, so I really wanted to put my best foot forward. I didn't feel like the EP was going to do that for me."
Instead of scrapping everything, she doubled down, writing new songs while filming the second series of High School Musical on location in Salt Lake City, and trading files with Nigro at his studio in LA.
The result is Sour, a stunningly-accomplished debut album that (a) proves Drivers License wasn't a fluke and (b) devours genres with an indecent appetite.
Her current single, Good 4 U, channels Alanis Morissette's pop-punk vitriol; Deja Vu finds her taunting her ex-boyfriend over waves of crashing drums and distorted guitars; and Enough For You is the sort of grippingly-told guitar ballad that made Taylor Swift a household name.
Swift is an important touchstone. Her intricate, inter-linking narratives have clearly influenced Rodrigo's writing and, like Swift, the star has a knack for excavating the little observational details that bring a song to life.
On Deja Vu, she recalls singing Billy Joel with her ex (Uptown Girl was their song) and how she's driven crazy by the thought of him sharing it with someone new.
Jealousy, Jealousy, meanwhile, tackles the inferiority she feels after being confronted by the "paper-white teeth and perfect bodies" of celebrities on Instagram.
"I wrote that song at a time when I was borderline addicted to social media and I just felt crippled by the comparisons," she says.
"I don't feel that now, but it's something I wanted to talk about. I am someone who has somewhat of a large following, so I think it's cool that I can be like, 'Yo, I still hate myself. I still compare myself to other girls.'
"Whenever I see people on Instagram do that, it always feel empowering to me - so I hope that I could be that for somebody else."
Jealousy, Jealousy isn't alone in exploring Rodrigo's negative thoughts. Anger, resentment, insecurity, spite and sadness are woven through her lyrics. They're not always pretty, but she wanted to expose the bewildering turbulence of being a teenager.
"I'm proud of the fact that I didn't shy away from those emotions," she says. "They're so uncomfortable to feel and definitely uncomfortable to talk about. Nobody wants to say, 'I'm super-insecure', or 'I'm really angry', but it was necessary for me.
"When I write my sadness down in a song, it feels manageable. It's like, 'OK, now I feel I can get through this.'"
Until recently, Rodrigo had the unique experience of becoming a household name without having to leave the house - an experience she calls "a blessing in disguise".
"It helped me keep my sanity when there was so much drama going on. Being in isolation with people I loved and cared about kept me out of the hullabaloo."
She's speaking a few days before her first-ever live performance for an audience, which took place at last week's Brit Awards. For the privilege of playing in the UK, she's been locked in a hotel room for a week, somewhere outside London.
"I'm not sure where, but it's beautiful," she beams, sitting in front of a neatly-pressed bed and floral wallpaper, as a chorus of birds threatens to drown her out.
"They're so loud! Even at 4am, I was awake, because jetlag, and the birds were chirping away. I was like, 'Wow, I guess this is England!'"
Lockdown has had other advantages too. Under different circumstances, she admits, her debut album would still be months away.
"Had I been going to press junkets, and performing on late night [TV], I wouldn't have had the confidence in writing the record that I did."
Even so, she feels like Sour is the work of a younger, less polished version of herself.
"Oh gosh, I am so much happier than I was when I wrote all of those songs!" she exclaims, "but it's also really cool that I made something out of those feelings.
"And now I get to look back at them and be like, 'Ha-ha! I didn't know anything!'"