Led Zeppelin bassist John Paul Jones appeared in court to reject allegations that his bandmates had plagiarized an obscure instrumental rock song for their iconic hit "Stairway to Heaven."

Robert Plant, 67, and Jimmy Page, 72, are being sued amid claims they stole the anthem's melancholic opening guitar arpeggio from "Taurus," from the first album of long-defunct LA psychedelic rock band Spirit.

Jones, 70, told the Los Angeles jury on the fourth day of a federal copyright infringement lawsuit he had no recollection of ever hearing Spirit.    

The musician said he remembered first hearing what would become "Stairway" at a rehearsal room the band used in Hampshire, England, as he and guitarist Page worked up an early arrangement.

Spirit guitarist Randy California, who penned "Taurus," long maintained he deserved a songwriting credit for "Stairway" but never took legal action and drowned in Hawaii in 1997.

A lawsuit filed by his trustee and friend Michael Skidmore two years ago seeks damages and claims California deserves a songwriting credit so that he can "take his place as an author of rock's greatest song."

At stake in the closely watched legal action are potentially millions of dollars in royalties collected in the three years prior to the filing of the suit through this month.

Page, dressed all week in a black suit with his white hair in a ponytail, had told the jury on Thursday his chord progression had more in common with "Chim Chim Cher-ee" from the 1964 musical "Mary Poppins" than anything else.

Attorneys for Page and Plant called music expert Lawrence Ferrara, who said the only similarity between "Taurus" and "Stairway" was a "descending chromatic minor line progression" used by composers for more than 300 years.

"It's a musical building block," Ferrara testified, and "not a relevant similarity."    

Playing an electronic keyboard for jurors, the expert performed "Taurus" and "Stairway" side by side, explaining that the two were "dramatically different."

Zeppelin opened for Spirit when the hard rockers -- Plant, Page, John Paul Jones and the since deceased John Bonham -- made their US debut on December 26, 1968 in Denver.

But the surviving members have submitted testimony that they never had substantive interaction with Spirit or listened to 1967's "Taurus" before recording "Stairway" in December 1970 and January 1971.

The lawsuit lists disputes over 16 other Led Zeppelin songs, many of which were settled by giving the complainant a songwriting credit and royalties, including classics "Whole Lotta Love" and "Babe I'm Gonna Leave You."

The trial was adjourned until Tuesday.