He'd come to the end of a long day in the studio, one that had seen him fulfil a teenage dream. So Diaz Grimm decided to celebrate.
The Cambridge rapper cranked up the music as loud as it would go, jumped on to the giant mixing desk, took off his shirt, and pressed play on Foreigners - the new single he'd just finished.
"We listened to it so loud," Grimm says, laughing at the memory. "You could see another group through the glass that kept looking [at us] like, 'What are those guys doing in there?'"
Grimm had definitely been up to something. Chosen for Apra's annual songwriting initiative Songhubs, he'd spent the day writing and recording new music at Auckland's Roundhead Studios with American super-producer Mike Elizondo.
If that name doesn't ring a bell, some of the artists he's worked with will: Elizondo has produced hits with everyone from Eminem, Dr Dre and 50 Cent to Fiona Apple, Twenty One Pilots and Mastodon.
It definitely rang a bell for Grimm, who'd made a beeline for Elizondo as soon as he arrived at the studio for the week-long project.
"I told Mike the story of how The Real Slim Shady was the first rap single I ever learned all the words to, and How We Do was the first instrumental I tried to write to as a 15-year-old," says Grimm.
The pair got along from the start, when Grimm asked if he could kick off their session cranking up How We Do, The Game's 2005 hit produced by Elizondo. "It was a good start to the day," says Grimm. "He was down with the vibe."
That set the tone for the creation of Foreigners, Grimm's bouncy new single featuring the vocal talents Raiza Biza and Iva Lamkum that's out now.
It is, he says, a "fun, catchy banger" full of lines that reference Elizondo's hip-hop hits of the 2000s. It's also a change of pace after his 2016 album, the sci-fi-themed 2077, that charted the creation of a new civilisation after an apocalypse.
But Foreigners is more than a single. Elizondo has become something of a mentor to Grimm, inviting him up to his Los Angeles music studio earlier this year.
"I just sat down with Mike and told him what I want to achieve and got his thoughts, a second opinion, on how I'm going about things," he says. "It was a really good chat. It was inspirational but it made me feel a lot more comfortable about what I'm doing."
It made Grimm realise that if he's up on the mixing desk, jumping around with his shirt off, it's a sign he's made music that he - and his fanbase - will enjoy.
"Making this song with Mike really made me realise the direction I should be focusing on," he says. "It's been a real moment for me."
Who: Diaz Grimm
What: New single Foreigners, co-written with Mike Elizondo
When: Released tomorrow