25 years after publishing is for photos
Movies it's 50 yeras after publishing
and for music and books its 70-75 years after the authors death (Depending on where you are)
How the recording is stored doesn't matter much. So yes, the 20 rar files are still considered to be the song.
As I said, depends on where you are: Copyright gets enforced according to the laws of the place where the infringement takes place. For servers it's
not where the server is physically located, but where the person is who owns/rents it.
So: look up your countries laws/ask a lawyer. Hope that helped.

