What is Michael Phelps listening to on his trademark Olympics headphones?

Seconds before diving into the pool for his impressive leg of the 4x100m relay final on Sunday, Michael Phelps was still wearing his headphones.

The music is something of a pre-race ritual for Phelps, in addition to cupping. “I have walked out to race with my headphones on throughout my whole career and listen to music until the last possible moment,” he told the Guardian in 2005, just after winning six gold medals in the Athens Olympics. “It helps me to relax and get into my own little world.”

The routine seems to work pretty well. Phelps and his team won the relay, earning him his 19th gold medal – but it certainly received a lot of attention. Some worried the swimmer would accidentally jump in with his headphones on. Many coveted a warm-up playlist from the most decorated Olympian – sometimes with their own speculation.

Phelps hasn’t revealed his playlist this year – though the New York Times wrote that it is a mix of Eminem, Young Jeezy and the country singer Eric Church.

He told the Guardian back in 2005 that he likes Eminem, Dr Dre and Notorious BIG. He had even gone to a Snoop Dogg concert in that year and met the rapper the Game backstage. “I didn’t get to meet Snoop. He doesn’t ‘meet’ people,” Phelps said.

Rolling Stone published a few of Phelps’ warm-up jams in 2012. His “solid gold hits” included I’m Me and Right Above It by Lil Wayne – “That song made me want to finish strong and look forward to life after swimming” – No Beef by Afrojack and Steve Aoki, Levels by Avicii and Go Getta by Young Jeezy.

Phelps and the rest of the USA swimming team did their own take on James Corden’s popular carpool karaoke segment ahead of the games – though it’s unclear if they used his personal playlist. With Phelps at the wheel, he sang along to Chicken Fried by Zac Brown Band. Even a phone call from his mom couldn’t interrupt Phelps from jamming out.

During the race in Rio, Phelps sported Beats headphones – a departure from his previous brand of choice, Sol Republic. After he wore Sol headphones at the 2012 Games, the brand came out with a line of Phelps-inspired headphones. In a video from Sol Republic, the swimmer said his first cassette was Green Day and he likes to listen to hip-hop in the morning and techno before workouts. With both sets of headphones, Phelps had to cover the logos with tape for the cameras.

Phelps’ son was seen emulating dad at the race on Sunday. The three-month-old Boomer Phelps wore noise-canceling headphones from the stands as he napped in the arms of his mom, Nicole Johnson. Boomer’s Instagram shows him in adorable patriotic outfits and has more than 100,000 followers.