The jazz trumpet star and the singer love to retell the story of how Morrison plucked a 17-year-old Pask from her school band at Kirrawee High in Sydney's south to perform on stage with him afterwards.

"I thought he was staring because my shirt was untucked – I was always getting in trouble for that," says Pask, now 37. Instead, the jazz veteran had been blown away by Pask's voice and that night was the start of a partnership that has taken the pair all over the world to perform to packed venues.

Says Pask: "When I want to annoy him I say he's a father figure, but really he's more like a big brother – a musical and life mentor. He's guided me through some ups and downs and we know each other inside out."

Their current tour, which has already taken them to Brisbane and Melbourne, combines their talents with a full big band and swing classics from Gershwin, Miller, Sinatra and Ellington.

Morrison is relishing the experience. "As far as jazz goes, this is as big as it gets," he says. "I don't know an artist who doesn't get a smile on their face when a big band fires up behind them."

He says he and Pask, who he says is like his "little sister",  can't wait to play the Sydney show. "It's home for both of us. It's going to be a good time."

James Morrison and his Big Band Tour is at Sydney Town Hall, Saturday 20 September 7.30pm