John Farnham's son says the Aussie icon still sings following his oral cancer surgery - after it was revealed he will never perform live again

John Farnham's son Rob has revealed the legendary musician still sings at home, despite undergoing several surgeries for oral cancer in recent years.

The Australian icon, 77, revealed earlier this year that he would never perform live again following his health issues.

However, his oldest son Rob, 45, told A Current Affair on Friday that his famous father still belts out a tune at home for his grandson Jett.  

'He's so good, he's back to his old self. You know, super fast talking. When I call he's like, "Hey Robbo, how are you, mate?"' Rob said.

Rob went on to reveal that the You're The Voice singer spends a lot of time with Jett, who is the child of his second son, James Farnham.   

'He chases [Jett] around the house and plays with him, they sing little songs and they give each other thumbs up,' Rob explained.

'He sings to Jett all the time. He sings all the jingles on the TV. Every now and then he'll belt out a big note. 

'The voice is still there, it's just doing shows and big stuff like that is not something that he can do, but he can still sing. He'll never lose that.'

Speaking earlier this year, John admitted the lasting effects of multiple surgeries to his mouth and jaw had made performing impossible.

'We can rule that out,' he said.

'Because of the surgeries to my mouth and face over the past few years, singing on stage is not something I can consider again. It's just not possible.'

Despite stepping away from live performances, John remains at the centre of a tribute concert celebrating his extraordinary career while raising money for a cause close to his heart.

The Songs of John Farnham: A Living Legend – The Celebration Concert will take place at Melbourne's Rod Laver Arena on Sunday, with proceeds supporting Head and Neck Cancer Australia.

The star-studded event will feature performances from an impressive line-up including Celine Dion, Hugh Jackman, Keith Urban, Tina Arena, Jimmy Barnes, Mahalia Barnes, Richard Marx, Kate Ceberano, Human Nature, Jessica Mauboy, Jon Stevens, Diesel, Mitch Tambo, Jack Jones, Mark Vincent, Ross Wilson, Hans and Ruby Rodgers.

Demand for the event has been overwhelming, with tickets selling out within hours of going on sale earlier this year.

John initially resisted the idea of a tribute concert before changing his mind when organisers explained it would help raise funds for Australians battling head and neck cancers.

The beloved entertainer has described the support from fellow artists as 'truly humbling'.

The Australian icon's health battle began after his wife Jill urged him to have a persistent mouth ulcer examined.

Doctors discovered a cancerous tumour, leading to a gruelling 12-hour operation in which surgeons removed part of his jaw and reconstructed sections of his face.

He later endured eight weeks of radiation treatment before eventually being declared cancer-free.

In his memoir, The Voice Inside, John revealed the devastating toll the surgeries had taken on the voice that made him one of Australia's greatest performers.

He explained that the reconstruction left him unable to open his mouth properly and robbed him of the movement needed to produce the sounds required for singing, describing the experience as both painful and deeply confronting.

Fans will also have another opportunity to celebrate John's remarkable legacy later this year when Whispering Jack: The John Farnham Musical premieres in Sydney.

Created to mark the 40th anniversary of his record-breaking album Whispering Jack, the production has been developed by Sydney Theatre Company, the Michael Cassel Group, TalentWorks and writer Jack Yabsley, and promises to honour the extraordinary life and career of one of Australia's most cherished entertainers.