Coldplay singer reveals how Shane Warne introduced him to John Farnham

Coldplay has sold out stadiums around the world, but the band's lead singer has declared that he can't compete with Australian music legend John Farnham's voice.

International and Australian performers came together to celebrate Farnham's music career at a charity concert in Melbourne last night, raising money for head and neck cancer.

Coldplay frontman Chris Martin recorded a special song to be played at the concert called A Better Singer Than Me.

"I'm really sorry I can't be with you," he told a sold-out crowd at the Rod Laver Arena show. 

"John, I send you all my love.

"Shane Warne is the person that told me about how great you are. 

"And this is a song about that and about you."

Farnham's son, James Farnham, said in a social media post that the original song was a "wild" surprise.

"I knew Chris Martin was doing the show, but I had no idea what he was actually doing," he said.

"This video is me out in the crowd, watching it for the first time. 

"I still can’t believe he wrote a song for my dad."

The song explained how Martin was introduced to Farnham's music during a trip to check in on bushfire-impacted communities in Victoria after the devastation of Black Saturday in 2009.

"My friend Shane said to me, 'There's been a bloody big bushfire. It's something you should see. I'm going in up to Kinglake to check on how they are and I made us a mix tape, we can listen in the car'," Martin sang.

"'And I really do love Coldplay. I love Coldplay, it's true. But my favourite is John Farnham, he's a better singer than you'."

Farnham performed You're the Voice, backed by Coldplay, at the Sound Relief concert at the SCG in 2009 to raise money for communities affected by the Black Saturday bushfires.

Martin also referred to this in his song, with tongue-in-cheek lyrics saying singer-songwriter Natalie Imbruglia suggested that Farnham would be the better choice to lead a relief show.

"She said, 'Here's what you can do. You can call John Farnham, he's a better singer than you'," Martin sang.

Farnham was unable to attend the Melbourne concert due to deteriorating health, with his family releasing a statement on the weekend.

His star power was still felt during the show, as other entertainers took to the stage to perform beloved songs from the 77-year-old's catalogue.

Jessica Mauboy, John Stevens, Jack Jones, Mahalia Barnes and Human Nature opened the show with a medley of Farnham songs.

Hugh Jackman and Celine Dion were also beamed into the arena from abroad, both performing Farnham songs that had inspired them.

Martin sang that Farnham's songs would keep living even once "we've all gone".