In the end, it was a Kiwi-born actor, Jay Laga'aia, who nominated the 1934 Australian children's song Kookaburra Sits in the Old Gum Tree and collected the points. His turn as a Play School presenter had stood him in good stead, but even he required prompting. At the CBD headquarters of Larrikin Music Publishing, managing director Norman Lurie had never noticed it either.

But when he got a call from a friend the following day, his ears pricked up. Larrikin had owned the rights to Kookaburra since the 1980s when it bought them for $6100 from the family of its late composer, Toorak School teacher Marion Sinclair. It was Lurie's job to find examples of its unauthorised use. ''That's what my life has become since 1990,'' he said last week. ''Trawling through songbooks and places where it appeared. It's so difficult unless you are a publisher to know where your work is being used.''

Two weeks after that Spicks and Specks episode, a flurry of legal letters arrived at Sony BMG Music Entertainment and EMI Music Publishing pointing out the similarity to the owners of the Down Under record and the score. A month after that, the Australasian Performing Right Association, which collects fees every time a song is played on the radio, at an event or by a covers band, was asked to suspend 50 per cent of its payments for Down Under.

An attempt to rewrite Australian music history had begun. If successful, it would take some of the shine off Men At Work's achievement in creating a No.1 song in Australia, the US and Britain, and reallocate some of the lucre it still generates through record sales, radio play, Qantas advertisements and films such as Finding Nemo and Kangaroo Jack. It could also change the way Australian musicians go about writing music and recording it, according to some experts. Almost two years later, the dispute came to a head in the Federal Court last week. Larrikin and its lawyers, Simpsons Solicitors, called it a ''David and Goliath battle'' over the genesis of one of Australia's favourite songs - our ''other national anthem'', as one witness called it.

Four days of legal inquiry and musical demonstrations explored what it was that made the song so successful, whether the Kookaburra echo was identical or adapted, how often it was played and how often left out, and even whether footage of flautist Greg Ham sitting in a mangrove tree beside a koala was an obvious reference to the 1934 song's full title or just the serendipitous result of a $6000 music video shot in the seaside suburb of Kurnell. ''A tree isn't a natural place to play a flute, you would agree?'' Richard Lancaster, SC, asked Men at Work's lead singer Colin Hay.

''What is a natural place to play a flute?'' came the reply. For some, Larrikin's suit will be seen as a brazen and opportunistic attempt to parlay the purchase - for a song - of a folk ditty into a 50 per cent share in one of biggest pop-rock hits ever penned in Australia. But the law is the law, and the Copyright Act says you cannot reproduce a substantial part of another's work and exploit it to make money without permission.

Larrikin says it was a clear exploitation - conscious or otherwise - of two out of four bars of Kookaburra, which Men at Work and their recording and publishing companies parlayed into a small fortune. The melodies are identical, its lawyers argued, and Men at Work in fact used more than half of the earlier song in a qualitative sense because they borrowed the ''signature'' opening.

Hay and EMI Music Publishing say Kookaburra is such a short song that borrowing anything from it could be called a substantial part. The key, harmony, structure and rhythm of Down Under's famous riff changed the sound of it so much that nobody - not the band, Lurie, or even five out of six Spicks and Specks panellists - noticed it until someone turned it into a quiz show question this decade, their lawyers argued. ''There is an obvious contradiction in the applicant's case,'' David Catterns, QC, said.

Hay and flautist Greg Ham, who improvised the flute riff in rehearsals, deny they consciously copied anything. They only realised the similarity sometime around 2002, they said, after which Hay sang the opening words to Kookaburra at live gigs from time to time for a laugh. Sony BMG, which owns the rights to the recording of Down Under, settled out of court with Larrikin before the hearing with EMI began.

The song's co-writer Ron Strykert, who was reportedly arrested in California in February for making threats against Hay, did not defend the claim. Hay's affidavit said they no longer had much contact and the reasons were confidential. ''I have no prospects of being able to ask Mr Strykert to appear in this case,'' he said. But EMI and Hay are determined to fight to the end, even if it means appealing against Justice Peter Jacobson's pending decision, sources said. Justice Jacobson, who clearly enjoyed the volley of musical performances that echoed around his courtroom last week, must now decide if the unofficial anthem of Australia's 1983 America's Cup victory is an example of piracy or homage: a copyright infringement, or a fair use and adaptation in a ''robust'' music industry imagined by the drafters of Australia's copyright laws.

The reuse of riffs is as old as rock'n'roll. And it's a good thing, according to Martin Armiger, former member of the Sports and composer of music for The Secret Life of Us and Young Einstein.

The 1955 hit Louie Louie by Richard Berry became the template for hundreds of songs including the Troggs' Wild Thing and the Beatles' Twist and Shout, he pointed out in his expert evidence for Men at Work and EMI. With the advent of digital sampling, sounds such as the infectious funk of James Brown's rhythm section were widely borrowed until Brown's record company began suing for it. More recently, the easy availability of sound editing software has spawned a genre of ''mash-ups'', where DJs overlay two very different hits to create a surprising new result, providing what Armiger called ''some of the more interesting (if questionably legal) music of our time''.

But mashing aside, most of the samples or references we hear in today's songs are the result of a negotiation between the creator and the adaptor. Agreements range from free use to 100 per cent of royalties, and permission can be used as a negotiating tool. The notoriously protective Madonna, for example, reportedly allowed Australian band the Avalanches to sample her song Holiday in the hope they would sign with her label.

Larrikin claims 40 to 60 per cent would have been a fair deal if the band had sought permission in 1979, arguing Kookaburra was very well-known and Men at Work not so. How much the writers, recorders and publishers of Down Under have made from it is yet to be investigated. Asked if the money had been spent, Hay, who moved from Scotland to Melbourne as a teenager, replied with typical Scottish understatement: ''I tend to make a good dent in it.''

''There's an old saying, 'Where there's a hit, there's a writ', '' says Professor Jill McKeough, dean of law at the University of Technology, Sydney and an intellectual property expert. The courts have been reluctant to interpret copyright law too heavily against new works, she said, for fear of stymying creativity - but the music industry will be anxiously awaiting the outcome of this case.

''It does create uncertainty about how people can reference other songs … It means you can never have a thought or write a song without looking over your shoulder. Musicians would have to start retro-fitting their songs with some kind of analysis.'' McKeough said the protection of creative works had to be balanced by the knowledge that ''nothing is truly original, there are so many songs in the world''. Armiger was particularly anxious about the implications of a Larrikin win. He wondered: ''What purpose is served by insisting on the rights of a dead composer against quotation, one who in her lifetime wasn't at all protective of her copyrights, who gave her intellectual assets away for no charge and showed no inclination to profit materially from her inventions?''



BITTER SWEET HARVEST FOR INDIE HEROES

For the 1997 hit Bitter Sweet Symphony, the English band the Verve (singer Richard Ashcroft) signed over 50 per cent of profits from the song to the Rolling Stones in exchange for the right to use a sample from the 1965 recording of The Last Time.



When they used too much, the copyright owners sued and the Stones ended up receiving all royalties and writing credits.



Asked in 1999 if it was a fair result, the Stones guitarist Keith Richards said, ''I'm out of whack here, this is serious lawyer shit.



If the Verve can write a better song, they can keep the money.''

COLD HARD CASE OF BORROWED BASS

Vanilla Ice's 1990 - and only - hit, Ice Ice Baby, borrowed the bass line from the 1981 song Under Pressure by Queen and David Bowie without permission or attribution.



The case never went to court, but Vanilla Ice reportedly reached a confidential settlement with Queen's lead singer, Freddie Mercury, and Bowie.



They were later credited for their role in the creation of Ice Ice Baby.



A BEATLE CREATED SWEET JUSTICE WITH THIS SONG



The Beatles' guitarist, George Harrison, above, paid an out-of-court settlement over his 1970 song My Sweet Lord, which a New York judge found had unconsciously infringed the copyright of the Chiffons in their 1963 hit He's So Fine.



Harrison was so incensed at the way the court dissected his work that he wrote a song about it, called This Song.



In the music video, he played in a courtroom along with the session drummer, Jim Keltner, as the judge, and Ronnie Wood from the Rolling Stones, interjected with the words, ''Could be Sugar Pie, Honey Bunch. No, sounds more like Rescue Me!''