The EU's top court on Monday issued a ruling on a 20-year copyright battle between German electro-pop pioneers Kraftwerk and rap artist Moses Pelham.
Pelham produced a track for singer Sabrina Setlur in 1997 called Nur mir (Only to Me), which Kraftwerk claims looped in a two-second clip of its 1977 single Metal On Metal.
Setting strict rules on sampling, the European Court of Justice (ECJ) ruled musicians cannot "sample" others' work without permission.
The case reached the ECJ after it passed through every level of the German judicial system.
Kraftwerk originally brought the action against Pelham and fellow producer Martin Haas in 1999.
Germany's Federal Court of Justice (Bundesgerichtshof) in 2012 judged Setlur's song should no longer be promoted saying it amounted to copyright infringement.
However, in 2016, the German Constitutional Court (Bundesverfassungsgericht) ruled the effect on Kraftwerk did not outweigh "artistic freedom".
The case was returned to the Bundesgerichtshof upon appeal, which referred to the ECJ for clarification.
The Federal Court of Justice will now take the final decision on the case.
What does the ECJ ruling mean for musicians?
The EU top court's ruling means the original producer of an existing recording must approve any reproduction of a sound sample being used in a new song.
However, it also deemed that modified samples unrecognisable from the original could be used without permission.
This may apply to Pelham's track — the disputed two seconds are a drum sequence that is looped repeatedly in Nur mir.