Spirit, the band that took Led Zeppelin to court and lost, are appealing the decision.
The plaintiff, Michael Skidmore - who represents the estate of late Spirit guitarist Randy California - claimed Led Zeppelin's 'Stairway to Heaven' ripped off Spirit's song, 'Taurus'.
A jury last year thought otherwise, throwing the case out.
But Skidmore has now filed an appeal, saying it wasn't fair the jury wasn't allowed to listen to 'Spirit' in court.
"The trial court refused to let the jury hear the full and complete composition of 'Taurus' embodied in the sound recordings that Jimmy Page possessed, instead limiting the comparison to an outline of the 'Taurus' composition in the deposit copy lead sheet."
In other words, the jury had to rely on the sheet music.
Skidmore's appeal also says the prosecution weren't given enough time to present their case, and a musicologist who testified on behalf of Led Zeppelin had a conflict of interest.
The court also "seriously erred when defining originality", according to the appeal.
Led Zeppelin songwriters Page and Robert Plant said last year they'd known "for 45 years" that 'Stairway to Heaven' was an original composition, despite years of talk it was - like many of the band's other songs - based on someone else's music.
Wolfe, who wrote 'Taurus', died in 1997. He never showed any interest in suing Led Zeppelin, but did call it a "sore point" that Led Zeppelin never acknowledged the similarities.