When they're not fighting over leather jackets or when to watch the latest One Direction film, the Haim sisters live in three-part harmony.
Backstage at the St Jerome's Laneway Festival in Singapore, the Californian pop trio dished up a note-perfect rendition of Second Hand News during a discussion of their favourite Fleetwood Mac songs.
While they could all agree that Lindsey Buckingham's opening salvo on Rumours is a pretty rad song, don't ask the sisters - Este, 27, Danielle, 24, and Alana, 22 - for a favourite Beyonce track.
Alana freaks out but eventually settles on Halo, while zany eldest sister Este goes for a controversial answer - Check On It.
"Whoa! What? Like, from the Pink Panther soundtrack," Alana exclaims. "Damn."
The sisters, whose performance as Haim with drummer Dash Hutton was a highlight of Singapore Laneway, might be living up to ditzy Valley Girl stereotypes. In reality, they're just super stoked to be back out on the road, playing Singapore for the first time and about to return to Australia.
Haim hit our shores last year for the Splendour in the Grass festival. During the visit, they put the finishing touches on their excellent debut album Days Are Gone, which was released in September.
"We had been a band for so long, we had never put anything out," Alana says. "Then to come to Australia and to see how the people were so excited and knew the words for (2012 debut single) Forever, it was a breathtaking, crazy, surreal experience."
Danielle, who says little during the interview, adds: "That's where we finished the record, so it's always going to be part of our history."
Before Singapore, Haim played shows in Japan, while the Aussie visit for Laneway will be closely followed by a tour of Europe.
It seems that 2014 will be as busy as 2013, which ended with the band playing their hits, The Wire and Don't Save Me, on US television staple Saturday Night Live.
"I'm so excited about it, are you kidding," Este says of the work ahead. "It's going to be awesome."
"Our whole lives all we wanted to do was tour," Alana adds. "And we were stuck in LA playing every type of venue or show we could play."
"Our devious plan is 'How do we get to see the world together and have fun doing it'," offers Danielle, who toured with Julian Casablancas, Jenny Lewis and Cee-Lo Green before firing up Haim. "So, we put together a band and we get to do that."
They argue often, as sisters do - "Just every day that ends in 'y'," Este jokes - but they have a relationship forged as much by the hours and hours spent practising and playing as by blood. They started out in family band RockinHaim before kicking out their parents.
Haim also share a love for the same kinds of music.
"I got my (driver's) licence and I really wanted to go see live music in LA," Este says. "My friends didn't have the same taste in music as I did, but Danielle and Alana did, so I wrangled them to come along so I wasn't a weird loner at a show by myself. I think that's how we became close."
Days Are Gone made Haim one of the coolest bands on the planet in 2013 and the sisters are already working on a follow-up.
"The rule of thumb as a musician - always record," Este says. "Always have some kind of recording device with you.
"We were on the airplane the other day and Danielle came up with something. She was like 'I can't find my phone, give me your phone'. I think that's important.
"Being on the road is inspiring and meeting new people and seeing new things, it's hard not to be inspired by those things," she says.
"Now is the time to explore," adds Alana, who says the experiences on the road will filter into the next record.
"Above everything else is that we're sisters," Danielle says. "We have a lot of fun together. This stuff, it doesn't feel like work."