Young, who has died aged 79, became best known as the host of the long-running Young Talent Time, which ran from 1971 to 1988 - outstaying Ian "Molly" Meldrum's Countdown (1974-1987).
The show introduced future stars Tina Arena, Dannii Minogue, Jamie Redfern and Debra Byrne to the public among its 40 cast members.
Prime Minister Anthony Albanese was among the first to pay tribute to Young in a post on X.
Tina Arena also issued a statement, saying she was struggling to process the loss of her mentor.
But as the prime minister hinted, the success of Young Talent Time had the effect of obscuring Young's contribution as a recording artist.
His legacy was already secure.
"He had a lot more strings to his bow than Young Talent Time," music writer Clinton Walker told AAP.
Walker pointed out that as well as writing and performing hits of his own, three of Young's songs topped the Australian charts, with another national No. 2.
The biggest was The Real Thing, written for Young's friend Ronnie Burns in 1968 until producer Molly Meldrum heard it and insisted Young give it to his client Russell Morris instead.
The seven-minute song, written as a reaction to a Coca-Cola jingle, was a smash that became an Australian standard, added to the National Film and Sound Archive's Sounds of Australia registry in 2013.
Walker said Young - after the Easybeats and the Bee Gees - was among the first Australian songwriters to emulate the Beatles by writing songs himself.
Ironically, his biggest solo hit was cover of the Beatles' All My Loving, which reached No. 4 nationally.
Performed as a slow ballad, it became beloved as Young Talent Time's closing credits theme.
But Walker said Young's "warm and cuddly" persona - while perfectly suited to television - made him less convincing as a rock star and he began to concentrate on writing for others.
Young wrote his second No. 1, The Star, for Ross D Wyllie in Australia before being covered by Herman's Hermits as Here Comes the Star, reaching No. 33 in the UK charts late in 1969.
Smiley, written for Burns, was about their friend Normie Rowe's conscription for the Vietnam War, peaking at No. 2 on the Australian charts in 1970.
Rowe later recorded his own version.
A month later came I Thank You, a No. 1 hit for champion boxer Lionel Rose.
Young was born in the Netherlands as Johnny Benjamin Arthur de Jong on March 12, 1947 before moving to Australia as a child.
By the age of 18, he was already hosting his own TV show in Perth, Club Seventeen, while putting together his own bands - Johnny Young and the Strangers, and Johnny Young and Kompany.
With Kompany, he toured with the Easybeats in 1966.
After splitting as a solo artist the following year, he supported the Rolling Stones, Roy Orbison, the Walker Brothers and the Yardbirds.
In the meantime, his TV career continued to flourish.
He began hosting The Go!! Show in 1967 after the resignation of future game-show compere Ian Turpie, winning his first Logie award as Best Teenage Personality.
When the show was axed, he moved to London, sharing an apartment with the Bee Gees' Barry Gibb, who encouraged him in his songwriting.
Young's family confirmed his death in a statement on Friday, saying he had a short battle with pancreatic cancer.
"Johnny leaves behind his wife Marisha, sister Cornelia, daughters Anna and Fleur, son Craig (dec.), seven grandchildren, and two great-grandchildren.
"The family respectfully asks for privacy during this difficult time.
"Details of a memorial service will be announced soon."
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