Led Zeppelin's Robert Plant and Jimmy Page must face a US jury trial over whether or not they plagarised the distinctive opening chords of their 1971 classic, Stairway to Heaven.

Last Friday a US District Judge, Gary Klausner, said Stairway to Heaven and the 1967 instrumental Taurus by the band Spirit were similar enough to let a jury decide whether Plant and Page were liable for copyright infringement.

The trial is scheduled for May 10th and the lawsuit was brought by Michael Skidmore, a trustee for the late Randy Wolfe, who was also known as Randy California. He was Spirit's guitarist and the composer of Taurus.

Skidmore said Page may have been inspired to write Stairway for the Led Zeppelin IV album after hearing Spirit perform Taurus when the bands toured together in 1968 and 1969, but that Wolfe never got credit.

The defendants said Wolfe was a songwriter-for-hire who had no copyright claim, and that the chord progression was so cliched that it did not deserve copyright protection.

But the judge said a jury could find "substantial" similarity between the first two minutes of each song, which he called "arguably the most recognizable and important segments" of the tracks.

"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," Klausner wrote.

"What remains is a subjective assessment of the 'concept and feel' of two works . . . a task no more suitable for a judge than for a jury."

Klausner dismissed claims against Led Zeppelin bassist John Paul Jones and Warner Music Group Corp.

He also said the trustee can get only 50% of any damages awarded, citing a 1967 contract that Wolfe signed.