Led Zeppelin spent the late 1960s and most of the seventies soaring to the highest heights in rock 'n' roll. But to reach the top, the band liked to climb up the shoulders of giants – sometimes crediting them, sometimes not. Members of Led Zeppelin have seen a whole lotta legal threats in their lifetimes, facing frequent challenges to their blues-rock anthems' authorship.

Next month, they'll be going to California to fight a jury trial defending the origins of Stairway to Heaven, their signature song and a staple of classic-rock radio. A trustee for Randy Wolfe – a songwriter in the rock band Spirit who went by Randy California and died in 1997 – is pressing the United States District Court in Los Angeles to give Mr. Wolfe a writing credit for Stairway, alleging vast similarities between its intro and the Spirit instrumental song Taurus.

Victory would posthumously put Mr. Wolfe in rock's pantheon, in addition to securing damages and, potentially, a share of future royalties to one of the most-played songs in rock history. But the result of a jury trial beginning June 14 – assuming the case isn't settled earlier – could also have vast implications for the future of copyright and musical creativity.

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Taurus / Randy Wolfe / 1968 The 1968 instrumental, ‘Taurus’ was released on Spirit’s self-titled debut album. Listen from 0:44 2:35

Stairway to Heaven / Jimmy Page and Robert Plant / 1971 Led Zeppelin’s iconic rock anthem has generated, by one estimate, more than $570-million (U.S.) since its 1971 release. 8:01

Last year, a California jury awarded nearly $7.5-million (U.S.) to the heirs of Marvin Gaye after they found that Robin Thicke and Pharrell Williams's contributions to the 2013 hit Blurred Lines bore enough similarities to Mr. Gaye's 1977 song Got to Give It Up that it infringed on Mr. Gaye's copyright.

Blurred Lines marked one of the biggest awards for music infringement to date. So, music-copyright experts are watching the Stairway case with keen eyes: Depending on the outcome, the huge sum given for Blurred Lines could either be downgraded to an anomaly in copyright history, or be remembered as the beginning of a culture of fear among music creators.

This, argues Charles Cronin, a University of California law lecturer who specializes in music copyright infringement, would have far-reaching implications to creativity by making artists fear their self-written songs might not sound original. Already, he says, the Blurred Lines decision "has made potential plaintiffs bolder, and it has inhibited innovation in the music industry."

Inspiration in music can be a fickle thing. There are only so many notes, melodies, words, instruments and rhythms out there; repetition is inevitable. Especially in hip hop, the culture of borrowing is practically celebrated through sampling: Building on the legacy of one's elders, so long as those elders are credited and compensated, is common practice.

In rock, and sometimes pop, originality is far more treasured. There is an irony here: Much of early white American and British rock music – especially that of Led Zeppelin – owes a world of thanks to the largely black music of the American South. Led Zeppelin has faced accusations of copyright infringement numerous times; some composers, including Howlin' Wolf and Willie Dixon, have been retroactively added to Zep songs' author lists for songs such as How Many More Times and Bring It on Home.

It's a mammoth of a song, but Stairway to Heaven begins with a gentle, slow, instantly memorable riff – one that bears a lot in common with the one that runs through Spirit's much-shorter Taurus. Both guitar parts rely on a slow, specific arpeggio played on a guitar with an intensely classical atmosphere.

How much these riffs have in common – and whether Taurus inspired Zep songwriter-guitarist Jimmy Page in writing Stairway – is what's up for debate. In April, Judge R. Gary Klausner wrote that "while it is true that a descending chromatic four-chord progression is a common convention that abounds in the music industry, the similarities here transcend this core structure." And so the lawsuit filed by Mr. Wolfe's trust, led by lawyer Francis Malofiy, is heading for a jury trial.

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There are many amazing facts about the case itself – according to court documents, for instance, Mr. Wolfe said in an interview before he died that it was "fine" for Led Zeppelin to use Taurus – but its result could significantly alter life for songwriters.

The Blurred Lines case is already rippling through society. As the case was being litigated, British pop artist Sam Smith bowed to pressure and partly credited Tom Petty and Jeff Lynne for his song Stay With Me because of melodic similarities to Mr. Petty's I Won't Back Down.

And intellectual-property lawyers have started fielding significantly more calls from writers alleging their own songs were infringed. "The number of 'fishing expeditions' has increased since the jury decision," Mr. Cronin said in an interview.

The Stairway case may rely on interpreting the original sheet music, as the Blurred Lines case did, along with statements from music experts. "There's going to be a lot of expert testimony about whether or not those relatively limited number of notes are commonplace," said Howard E. King, who represented Mr. Thicke and Mr. Williams in the Blurred Lines case, and is helming an appeal. "In which case the defendants would argue that if there's 10 or 20 or 50 other songs that use the same series of notes, that it's not protectable, it's commonplace, it's in the public domain."

But the vast majority of such copyright claims settle out of court, Mr. King said in an interview.

Mr. Cronin believes that's a plausible outcome with Stairway. These kinds of accusations are embarassing for artists by putting their integrity at stake. Led Zeppelin, he said, is "in exactly the position the plaintiff wants them: between a rock and a hard place."

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Ceding Stairway's authorship – even a fraction of it – would leave its original composers, Mr. Page and Robert Plant, with a deep wound. But for the lawyer behind Mr. Wolfe's trust, that would correct a longstanding injustice. "Randy never got the credit he deserved in his lifetime," Mr. Malofiy told The Globe and Mail.

If Stairway is found to infringe on Mr. Wolfe's copyright and a huge award is given, it could create a precedent-setting chill among songwriters worldwide. But Mr. Malofiy said his quest is about correcting history.

"It's never been about money," he said. He's willing to settle for a single U.S. dollar, so long as Mr. Wolfe is listed as an author. "If Randy California was part of Led Zeppelin, he would have been given equal credit with Page and Plant," he said.

CondéNast Portfolio magazine once estimated Stairway's total worth to be about $572-million (U.S.), although a three-year retrospective statute of limitations would give Mr. Wolfe's trust little of that. Still, the sky – heaven? – is the limit for the song's future value in royalties. Mr. Malofiy said any proceeds from the case would not go to building a stairway there. Instead, they'll be funnelled through the trust to fund musical instruments for underprivileged children in public schools.

The long, slow dance of Led Zeppelin's most famous song and its place in our popular culture

It's 1992, and Mike Myers's Wayne Campbell is in a music store, ogling a white Stratocaster in the movie Wayne's World. A long-haired clerk reluctantly frees the guitar from its case. Mr. Myers rests it on his left knee, and plucks four familiar notes before the clerk grabs the guitar's neck to silence it. He points to a blue sign across the room. It delivers a simple, crucial rule for clientele: "No Stairway to Heaven." Myers turns his head to face the camera. "No Stairway," he says, barely restraining a cheeky grin. "Denied."



Led Zeppelin released its fourth, nebulously titled record in 1971, and with it came Stairway to Heaven – the song that set the template for almost every rock ballad to come after. Unfortunately, that legacy also turned it into one of the most overplayed songs in history. By the time Wayne's World was released in 1992, Stairway was already so frustratingly cliché that it was taboo in many guitar stores.

With its Renaissance-style guitar-and-recorders intro, slow build and fierce rock conclusion, Stairway to Heaven spent years as a guaranteed closer to high-school dances. It still consumes the airwaves on classic-rock radio with its unmistakable riffs. Robert Plant's lyrics are even studied in schools as an example of metaphor in music.

The song has also weaved its way into pop culture in countless ways. It's popped up in The Simpsons (Homer: "I'm not looking for glory or wealth. I'm just buying that stairway to heaven Jesus sang of."), been spoofed by SCTV, become the name of a Korean TV drama, and served as a long-time muse for Jack Black's comedic band Tenacious D. (Anyone who's heard their song Tribute knows exactly what it's paying tribute to.)

After the first U.S. theatrical release, later versions of Wayne's World became a bit confusing. That guitar riff Mr. Myers plays in the music store is replaced by some nonsense electric shredding that sounds nothing like Stairway to Heaven – even though the clerk still points to the guilt-tripping, song-referencing sign. It's been reported that a licensing conflict forced the filmmakers to scrub the riff from the film – a copyright-protection move that seems ironic given the current court battle over the song's authorship. No Stairway for real. Denied.