Level 3, level 4, and level 5 music of the GOG release of Prehistorik 2 have some additional instruments that sound like a bug - particularly it is one music track that is present on those levels. This additional instrument sound was not present in the original game release. Probably that's an issue with sound drivers or something. Unfortunately, I cannot post links in the thread, but you can search the video on Youtube "Prehistorik 2 Strange instrument at 1:15" by McPollus.
Also, you can Google this issue "If I play the game from the TITUS cd-rom in DOS-mode there is an extra " instrument "." and find it on the Prehistorik 2 forum.
I vaguely suppose that is due to some bugs in the file "PRE2.SQZ".
Is there any fix?

P.S. If you want to hear the correct way on how the music on this level should sound like, find on Youtube "Prehistorik 2 Gameplay - Level 3" by "Shaddow Black0". I don't know what version of the game he used but the colors are also correct on that level.