Members of Led Zeppelin have appeared in court to face claims that they copied the famous opening guitar riff on their "iconic" song Stairway To Heaven.
Singer Robert Plant and guitarist Jimmy Page attended the hearing in Los Angeles after being accused of "lifting" the introduction of their classic 1971 hit from a track by psychedelic American rock band Spirit.
A lawsuit has been filed by Michael Skidmore, the trustee of Spirit guitarist Randy Wolfe - known by the nickname Randy California - who drowned in 1997 having never taken legal action over the song.
The copyright infringement trial is taking place before a jury at the US District Court, where Plant, Page and their bandmate John Paul Jones are expected to give evidence.
Mr Skidmore's lawyer Francis Malofiy told the hearing: "This case can be summed up in six words - give credit where credit is due.
"The pink elephant in the room is Stairway To Heaven is one of the most iconic rock songs. Led Zeppelin is one of the most iconic rock bands of all time.
"Our issue is where they picked up this piece of music."
Wolfe - who was nicknamed Randy California by his friend Jimi Hendrix - wrote an instrumental track called Taurus for the "love of his life" in the late 1960s, the court heard.
But the musical composition "fell into the hands of Jimmy Page", who used it for the introduction to Stairway To Heaven, Mr Malofiy said.
The lawyer told the court both songs used the same three pairs of notes - A and B, B and C, and C and F sharp - and featured chord progression that "keep the listener wanting more".
Both pieces of music were played to the jury of four men and four women during the hearing.
Mr Malofiy said he was "not denying the magic" of Led Zeppelin but that Stairway To Heaven "lifted a composition from a lesser known song".
"Jimmy Page and Robert Plant are incredible performers and incredible musicians but they cover other people's music they try to make their own," he said.
Led Zeppelin appreciated Spirit "on an intimate level" and played a cover of the "pioneering" US band's single Fresh Garbage 16 times at their concerts, Mr Malofiy said.
Led Zeppelin were also the opening act for Spirit when the British band made their US debut in December 1968 in Denver, he said.
Despite initially claiming he did not know Spirit, Page later acknowledged he liked the band, while Plant had been out socially with some members of the group, the court heard.
Page, 72, and Plant, 67, were dressed in suits during the hearing and sat next to each in court.
Led Zeppelin's lawyer Peter Anderson said: "Forty-five years ago Jimmy Page and Robert Plant wrote some of the greatest songs in rock 'n' roll history. One song was Stairway To Heaven. Now, nearly 50 years later, they are being sued over it.
"Stairway To Heaven was written by Jimmy Page and Robert Plant and them alone. Period. Enough evidence remains to show history cannot be rewritten."
Janet Wolfe, sister of Randy Wolfe, told the court her brother was "upset" about Led Zeppelin's alleged use of his song.
"It was something that upset him for many, many years," she said. "I wanted him to do something about it."
The hearing was adjourned until this morning.