The reason why RIOT had such a weird sound in the first place was that Sly was in the middle of one of the wierdest rides imaginable. The whole black/white thing was resulting in him getting leaned on by "certain parties", death threats, shakedowns, etc. Paranoia was high, and so was the coke use. So sly was carrying the tapes around with him, and was using them as "leverage" to get both coke, pussy, and safety. He was letting all kind of people lay down vocal tracks in exchange for whatever was needed at the moment. That's why there's so much tape hiss and degrdation of the final vocals. There's been literally hundred of passes made before the final vocals got laid down.
This is all from an article in some British R&B article whose name I don't remember. Would've been ca. 1992-94. The source was either Larry Graham or Freddie Stone. Best article I've ever read about Sly, bar none, and I was a total dumbass not to buy it.