Rap, the stripped-down, street-smart sass talk associated with urban wastelands like the South Bronx, has become popular music's most controversial form.

In its hard-core version it can be vicious and small-minded. It's almost invariably misogynous, and it shows a depressingly limited span of cultural reference points -- usually TV reruns, exploitation movies and hit records. Still, it's tough, candid and inventive, and at its most affirmative, it uses the very raw material of ghetto street life to transcend that existence.

Ironically, the rappers who have managed to offend the greatest number of parents, police and other enforcers of public taste are the Beastie Boys, a trio of upscale white kids who appropriated the sound for tracks like "Fight for Your Right to Party." Few of those who have fought for their right to ban the Beastie Boys or Run-DMC, however, have heard rap at its most harsh and unsocialized. And if they haven't heard the likes of Schooly D, they don't know the half of it.

Schooly D: 'Saturday Night!'

While some of the best rappers, despite their macho growls, come from middle-class backgrounds, Jesse (Schooly D) Weaver is an alumnus of a Philadelphia street gang called the Parkside Killers, whose exploits were the subject of "P.S.K. -- What Does It Mean?," the first Schooly D single to attract national attention. A new version of that track, "Parkside 5-2," is included on "Saturday Night! The Album" (RCA/Jive 1066-1-J), a retrospective of his earlier work that constitutes Schooly's first major-label album.

Schooly D's sound is as crude as his ghetto-gangster persona. Where other rappers construct complex hip-hop concertos for voice, beat-box and borrowed sounds, Schooly's best-known work is little more than a beat accompanying his foul-mouthed, ill-tempered rants. His latest single, "Housing the Joint," is built on the rubble of Sly and the Family Stone's "Thank You (Falettin Me Be Mice Elf Agin)," but Schooly's not as inspired a riff-thief as many of his contemporaries. He's best on stripped-down, self-explanatory tracks like "Dis Groove Is Bad" or "Get n' Paid" (in which he explains that he won't step on stage without cash up front).

Schooly's vehement recordings, which are almost entirely unquotable in a family newspaper, may have more documentary than esthetic value. Even by rap standards, his work is artless. Still, there's no denying that his harsh communique's crackle with a mean-streets vitality as fascinating as his confrontational world view is disturbing.

Kool Moe Doe: 'How Ya Like Me Now' Amid contemporaries -- from Schooly D to the almost-mainstream L.L. Cool J -- whose most common boast is how much money they're making, Kool Moe Dee comes across like a hip guidance counselor. With a little help from a riff from the Aretha Franklin classic "Respect," Kool rebukes his listeners that "some brothers will do anything for a bill" but "money won't buy respect." (That doesn't prevent him, of course, from closing the record with "Get Paid," his own entry in the how-fat-was-my-wallet contest.)

A former member of the Treacherous Three, Mohandes (Kool Moe Dee) Dewese is a veteran of the rap scene who's concerned with more than rap's traditional braggadocio, in which he nonetheless indulges in the entertaining title track of his new album, "How Ya Like Me Now" (RCA/Jive 1079-1-J). Kool's first solo album was notable for "Go See the Doctor," a cautionary tale of promiscuity's side effects. Here Kool's "Wild, Wild West" disputes the notion, promoted by rappers like Schooly D, that street violence is cool.

Recorded in London, "How Ya Like Me Now" is a showcase of deft aural collage: James Brown beats on the title cut, Queen on "Rock You," even Paul Simon on "50 Ways." The production is sophisticated without sacrificing the improvisational swagger that is central to rap's appeal.

Just Ice: 'Kool and Deadly (Justicizms)'

Just Ice also has an agenda that embraces more complicated topics, but it's hardly as benevolent as Kool's. Among the "Justicizms" on his new album "Kool and Deadly" (Fresh LPRE-5) are that eating pork is wrong ("Haven't you," he demands, "seen the way this animal lives?") and that any woman fortunate enough to go to bed with him -- not exactly his parlance -- "is sure to be glad."

Ice's curious puritanical streak comes into focus on tracks like "Mostitup" and "Lyric Licking," where he shows his affinity for reggae rhythms. Most of the record's tracks, however, are spare hip-hop, tough and raw but not especially distinctive.

Ice occasionally demonstrates a sense of humor: His introduction to "The Original Gangster of Love" helpfully inventories all the potentially objectionable words the listener is about to encounter, a list that includes just about every word the P.M.R.C. prefers not to hear on vinyl.

M.C. Shan: 'Down by Law'

Since it opens with the distorted voice of George Jetson crying "Jane, Stop This Crazy Thing!," M.C. Shan's "Down by Law" (Warner Brothers/Cold Chillin' 9 25676-1) would seem to be a lighter-hearted record than Schooly's or Ice's. "Jane" turns out to be an account of drug addiction, though, and "Down by Law" doesn't flinch from other unsavory issues.

Shawn (M.C. Shan) Moltke's persona is not quite so ferocious as that of some of his peers, but neither is his the voice of tolerance and reason. Though he admits the possibility of romance on "Left Me -- Lonely," Shan's attitude toward women is characteristically contemptuous. "Project 'ho" recounts Shan's embarrassment at being seen in the company of a notoriously promiscuous neighbor.

Shan experiments with reggae ("Another One to Get Jealous") and rap balladeering ("Left Me -- Lonely"), but he's best with the now-familiar scratches, samplings and throbs of hip-hop. Though his sound is not particularly innovative, Shan creates a wiry, visceral groove on such tracks as "Kill That Noise" and "Living in the World of Hip Hop."