In Kool Moe Dee's tome, There's a God on the Mic, which is sadly one of the few books that deals with the technical aspects of rap, there is a discussion of KRS-One's conceptual abilities. Given Kool Moe Dee's (and many other hip-hop critics') near reverence for KRS-One's abilities, he mentions that KRS-One is not always very conceptual, because he stays close to being a "quintessential MC...doing the rhymes about how dope he is". In other words, he is usually in the position of being himself, talking about himself, and not constructing characters and skits. Which isn't to say that he can't. The song "Hold", from his eponymous 1995 album, is an example of KRS-One being conceptual across multiple levels, laying out a puzzle that can be taken several ways.
The song is not well known, and is not a favorite even within KRS-One's fanbase, probably because it is too conceptual. The song ends each of its 39 lines with the same word, "hold" or "hole" or "whole". The tempo of the song is slow, and the melodic component is small, even for a rap song. The song verges on being a spoken-word poem, with the song barely raising above a monotone whenever KRS-One reaches the syllable "hold". The interest of the song, other than the audacity, comes from the many different uses and homophones KRS-One comes up with:
Half of me is sane and maintaining a hold
Suddenly I bump into some asshole
He's cursin' me out, but this pistol that I hold
Took control, and in his head I put a hole
Ahhh man, now I'm lookin' around the whole
So KRS-One on one hand uses concepts on the level of wordplay. Above that, the narrative has a concept, derived from the wordplay, about a man who has is trying to hold on to his sanity but finds himself slipping into a hole. The narrative is a story of the criminal life, caused by the fact that this man can't help but slip into the hole.The narrative is about as gritty as could be expected from this period of hip-hop but much less glamorous than most. KRS-One has a moralistic bent, which moves us into the third layer of conceptuality, the moral level of the song. After the conclusion of the song, where the protagonist is not only in prison, but in solitary confinement, KRS-One doesn't make us guess at the moral, but tells us:
The moral to the story is...your addiction to your needs and your
wants is what causes problems in your life.
The moral of the story is derived from the wordplay, with KRS-One suggesting that the "hole" of our needs, and the "hold" we put on objects to satisfy it, is the cause of our problems. As it is, the narrative and the moral could be seen as stark and simplistic, but further reflection on the moral presents a fourth layer of conceptuality, the possible esoteric interpretation of the song. KRS-One may be suggesting that human consciousness, and the problems it goes through, are caused by the fact that we have a basic need inside of us, and that we attempt to create realities to make up for this need. This may actually be a pronouncing of a concept of Emptiness and Being. This pronouncement is more curious when we reflect that this is all based on what seemed at first to be a simple case of wordplay.
So, if we do accept that KRS-One is trying to present four layers of conceptuality here, with word play, narrative, moral and esoteric concepts, we understand why he can be conceptually great when he wants to. The only other song that I can think of that is conceptual on these lines is Nas' I gave you power, and songs like these are why KRS-One and Nas are afforded such respect in hip-hop circles.