But they can't quite get it. After a few spluttering attempts, they give up.
As the strings fade out, Pene tells a stage hand: "We have so many versions of that song, we didn't know which one [to do]."
That's not the only thing holding them back. Sol3 Mio are New Zealand's biggest opera stars, and remain one of our industry's biggest acts, with three No. 1 albums to their name.
Kids love them. So do grandparents. The media does too. The night before tonight's rehearsals, Pene co-hosted The Project for the second time. While he's being mic-ed up for rehearsals, a stage-hand mentions a gag he made about the South Island. "Did you watch it?" he asks her, giggling nervously.
They've owned Spark Arena before. In fact, they've sold out the 12,000-seat venue twice over their seven years together – something Lorde, New Zealand's biggest pop star, is yet to do. They remain incredibly popular. "We could sell out Spark Arena again," Pene acknowledges.
But they've refused. On their new tour, Sol3 Mio are going against the grain by playing only intimate shows in front of smaller crowds. Pene says that decision is going to hit Sol3 Mio where it hurts. "It's the difference between hundreds of thousands, and tens of thousands," he says.
When most acts aspire to perform in front of the largest crowds possible, and make the most out of their career while they can, Sol3 Mio's decision to downsize is an odd one.
Why wouldn't they put on the "schtick," as Pene calls their much-loved comedy-opera routine, book more arena shows, and think of the money?
Pene was in a bad way. "Wow, I was hungover," he says, shaking his head at the memory from what would become the beginning of Sol3 Mio. He'd been in Whanganui, and stepping on stage was the furthest thing from his mind.
He'd been out the night before, celebrating with recent graduates from the New Zealand Opera School. Pene graduated the previous year, and was there as a guest.
"We got hammered," admits Pene. "The next day, they were like, 'Are you ready to sing?' I was like, 'Are you kidding? You didn't say I was singing!'"
Nervous, and feeling sick, Pene called Amitai and Mackay, who were also in Whanganui. "He was like, 'Guys, I'm not feeling too well,'" remembers Amitai. "'Come on, help me out.'"
They agreed on a song, Mackay grabbed his guitar and they rehearsed briefly on the side of the stage before stepping out. There was no plan to start a group, no thought given to the fact that they were about to begin their career together.
But that brief performance, captured in shaky hand-held camera on YouTube, is remarkable viewing. Over seven minutes, you can watch Pene shake off his hangover as the trio stun the crowd with their full-lunged, comedy-fuelled take on Luciano Pavarotti's O Sole Mio.
The approval is raucous and overwhelming, so much that they are asked to perform an encore. They hadn't planned on that either.
"It just about bought the house down," says Donald Trott, the executive chairman of the school they were performing in. The opera industry veteran was there, and remembers it well. "It was instantaneous and great fun."
As they got their standing ovation, Pene says a woman in the crowd yelled, "You should form a group!" at them. Their reply? "Ah, that's funny."
Several weeks later, however, they did exactly that, filling the Auckland Town Hall for their first show as Sol3 Mio. The gig was a fundraising effort for the trio to study at the Wales International Academy of Voice.
Despite Universal Music waving offers at them, they put Sol3 Mio on the backburner, and boarded a plane to Cardiff. Once there, they got an email from one of their early opera mentors. It wasn't complimentary.
"He had cc'd everyone in, Dame Kiri Te Kanawa, our music teachers, mentors, professors at the school of music … he went on this whole rant about how we're not serious opera singers [and were] chasing cheap fame."
Pene still bristles at the memory. "It just hammered us down." He says the mentor wasn't happy about Sol3 Mio giving contemporary pop songs operatic makeovers. "He thought it was a joke."
He's still not over it. In fact, it's a key reason for their intimate new tour.
Sol3 Mio love to wing it. "My biggest bane is getting set lists," says their manager, Scott Maclachlan, "because I'll probably get them the night before [the show]."
Their free spirit gives Sol3 Mio's live shows an off-the-cuff feel, like they're making it up as they go along. Often, they are. "There is no rehearsal," admits Pene. "It's scary and fun at the same time."
The trio rely on their training and chemistry to wow crowds. They've had plenty of practice. Pene and Amitai, both tenors, sang in churches and rest homes throughout their upbringing in Mangere; similarly, Mackay, a baritone, grew up performing for dementia patients. All have multiple qualifications and awards beside their name, and tour regularly as solo performers, outside of Sol3 Mio.
Their connection together is obvious, and instant. They struggle to explain it - it's just there. "We've had people join us," says Mackay. "Nine times out of 10, it hasn't worked. It's a weird block in energy."
On stage, they're a team, no matter what's going on behind the scenes. Sometimes they argue backstage, but that evaporates as soon as the show starts. "It's how we were raised, as Samoan Kiwis," says Mackay. "I was always beating the crap out of my cousins, my brothers were beating the crap out of me. As soon as Mum and Dad said, 'Get in the car, we're going to church,' there was no argument, there was no, 'I'm not going.' There was no escape route. It's the same with us, there's no exit here. As soon as that show starts, it's game on."
Emotions run high during their performances, which often run to three hours. Few acts can make crowds laugh with one breath, and cry with the next. "It's this roller coaster we take them on," says Pene. Sometimes, they get overwhelmed too. If that happens, they'll come to each other's rescue with a secret tap on the back, then taking over the song.
Sol3 Mio enjoy the kind of popularity most artists only dream of. But that's not all they're chasing. They want the opera world to respect them. "You can make lots of money," says Pene. "It's not what it's about for us. There's an integrity that comes from doing classical music, we don't want to conform to commercialism. We've got to show you what we can do best."
As he does regularly, Pene breaks into song. This one, though, is a little different. "Every little thing / Is gonna be alright," he sings, his warm, honeyed vocals dripping over the Bob Marley classic. Sol3 Mio have never covered that, nor Marley's Redemption Song, during a concert. They save those for themselves, singing them together while they were riding tour buses up and down the country.
It was their way of rebelling. Because during those "ginormous" tours, at the peak of their fame, they were struggling. "People say, 'You must have amazing times on tour,'" he says. Pene says both tours – 28 shows in 30 days on the first, 17 shows in 25 days in the second – reached a point where things felt like they were spiralling out of control.
"They were really hard times … they really take their toll. We felt we were getting lost in all this commercialism, and bigger powers trying to control us all the time. The label were saying, 'You should do this,' management were saying, 'You should do this.' We felt we lost our own creative process. These songs we'd sing on the road would ground us again."
That's why, on their Back to Basics tour, they've turned down arenas. At tomorrow's showcase at the Town Hall, they'll walk out on stage in front of just 1600 people. They haven't played there since their fundraising show in 2012, and it's the biggest gig they'll play this tour. It sold out within a week.
That's not all: at each show, there are no microphones, no big sound systems, just the three of them, "bare". They'll be more serious shows, with songs chosen to showcase their operatic skills. "They can hear you breathe. They can hear the mistakes. They know it's you. You can't hide behind nothing," says Pene. It's also about making sure their former mentor who wrote that email knows he was wrong.
"I trained for so many years to do this, to show people what I'm capable of," says Pene. "This is where we belong. That's where our voices soar. When people see raw talent, at its purest, they get mesmerised like no tomorrow. They say, 'How is this possible?' It's like seeing superheroes."
Sol3 Mio perform at the Auckland Town Hall tomorrow night (Sunday, March 17).
