Managed to finally solve the final piece recently in a doubly perplexing puzzle which consisted of two samples used on Andre Nickatina's rap song, I'm a Pisces.
Identifying their origins became something of an obsession ever since I first heard the song on an ancient rap forum. Had a hunch they were both sourced from films, but I was never 100% sure, however. Turns out I was right after all these years:
Chanced upon randomly watching The 7th Voyage of Sinbad (1958) on TV many years ago and hearing Bernard Herrmann's Cobra Dance was a eureka moment. The music in question occurs during the scene where the villainous sorceror, Sokurah, melds a handmaiden in a giant clay vase with a cobra, like a progenator to the Brundlefly. With the aid of Ray Harryhausen's ace stop-motion mastery, the snake woman dances before the sultan's royal court. Knew this wasn't some obscure song from a far off continent, but taken from a vintage Hollywood film. Took some years to finally realise it, though.
Would have loved it if the vocal sample from the start of the song was a similar discovery to the one above, but this was a lot more straight forward - Googling! Yes, it took decades until your host realised he could do a simple Google search. Lo and behold it turned out to be from a Fred Williamson film called Death Journey (1976). The dialogue in question appears at 58 minutes and 21 seconds into the film, but you can hear a part of it in the trailer, too. Thus, the final piece in the puzzle which has antagonised the little grey cells for so long has finally been laid to rest.