Led Zeppelin must go back on trial in a lawsuit that accuses the classic rock grandees of stealing the opening chords of “Stairway to Heaven" from an obscure 1968 instrumental.

A federal appeals court in San Francisco on Friday overturned a 2016 jury verdict that Jimmy Page and Robert Plant’s 1971 song didn’t use anything that was unique and original in “Taurus," a track written by late Spirit guitarist Randy Wolfe, whose trust brought the lawsuit.

Page and Plant both testified at the 2016 trial in Los Angeles about Led Zeppelin’s formative years, the band’s U.S. touring in the late 1960s and the genesis of “Stairway." Music experts testified that the descending chromatic scale in “Taurus," which the band was accused of having copied, is exceedingly common in popular music and isn’t subject to copyright protection.

The trust of Wolfe, who went by Randy California on stage, argued the trial was unfair because the jury could only hear an acoustic rendition of “Taurus," instead of the recorded version. Copyright protection at the time of composition only applied to the sheet music.

The appeals court’s ruling focused on the judge’s instructions to the jury and rulings about evidence.

The case is Skidmore v. Led Zeppelin, 16-56057, U.S. Court of Appeals, Ninth Circuit (San Francisco).

This article was provided by Bloomberg News.