Gangsta rap didn’t really start out too far afield of what was happening in hip-hop’s NYC origin points — and if it took deeper roots West of the five boroughs, it didn’t even need to be as far away as Los Angeles to do so. Philadelphia’s Schoolly D was more outwardly explicit, abrasive, even crass next to his circa-’85 New York peers like Run-D.M.C. and LL Cool J, but that just made him a powerful bridge between those emergent stars of East Coast rap’s 808 era and the West Coast permutations that gave us the likes of Ice-T and Too $hort. At its bluntest, his shamelessly profane button-pushing could result in a track as trollish as “I Don’t Like Rock ‘n’ Roll” — simultaneously a prescient underdog defense of a young musical movement against a rockist establishment, a dated, gay-baiting goof that the “Kashmir” sample on 1988’s “Signifying Rapper” rendered a moot point, and a track more interesting for its personality-building specificity than any genre clash the title promises. At its most effective, though, Schoolly D’s debut makes the case for rap’s vulgar side just by letting him do his own thing with a defiant, relentless confidence. The beats are vicious, compensating for its DIY-budget drum-machine simplicity with DJ Code Money’s omnipresent riff-warping scratches and a bass-kick-heavy reverb that sounds more King Tubby than King of Rock. And that booming, echoing pulse makes his voice sound like it’s carrying through a dozen city blocks as he turns Philly-local hood lore (“P.S.K. ‘What Does It Mean?’”) and stylistic claim-staking (“Gucci Time”) into god-tier shit talk that lands somewhere between Melle Mel and Rudy Ray Moore.