Watch Out. Cover versions?

Hello There. Caution is warranted. I have the MP3 collection due to the m. Bought M. n. Strong stock selection. At first listen I was a little surprised that the songs do not sound like the originals. Mutilated the digital "remastering": first guess? After repeated Listen I think, however, that they are cover versions. Per Se is not to denounce, but there is no indication.
Tip: the also offered "Bams 80 - NDW" receives original versions.