In December 1990, hip-hop magazine The Source published the first in-depth study of the then-nascent “gangsta rap” trend in a special issue. The cover story was unusually prescient, touching on nearly all the pivotal arguments and counter-arguments over violent rhymes that would reemerge in a few years as the debate eventually involved Congress, threatened multinational media corporations and inspired protests from all corners.

Throughout the piece, writer David Mills (who would go on to write for “The Wire”) lent a sympathetic ear to besieged young artists like the Geto Boys and Dr. Dre, but fretted over the direction the music was taking.

“Like radiation exposure,” Mills wrote, “it’ll be years before we really know the consequences of our nasty little entertainments.”

To modern ears, the sentiment seems almost quaint. It’s been a dozen years since Eminem’s “The Marshall Mathers LP” last galvanized anti-rap forces into a widespread outcry, and longer still since heavy metal was blamed for teenage suicides and occult rituals. These days, music just doesn’t seem to make people want to kill each other like it used to. Even the most recent round of hand-wringing over gunplay in media has almost solely targeted videogames and films: In his press conference following the Newtown massacre, NRA exec director Wayne LaPierre didn’t mention music once.

But Mills’ question is still worth considering. Two decades on, has the proliferation of violent gangsta rap and heavy metal noticeably warped the generation that (like this writer) grew up unwrapping Dr. Dre’s “The Chronic” at their 10th birthday parties? Judging by changes in crimes rates, quite the opposite — overall violent crime has actually been steadily declining since the heyday of gangsta rap, with homicide rates among African-Americans seeing some of the sharpest drops. (Of course, no reasonable person would take this to mean that the rise of gangsta rap caused a reduction in crime, though a corollary argument would surely be made were the numbers reversed.)

Culturally speaking, however, the question gets trickier. While heavy metal downsized and carved out a comfortable niche far outside the musical mainstream, gangsta rap — which conveniently emerged as Middle America’s favorite bugaboo just as the Satanic specter of metal was declining — has permeated the culture at large to a degree that is sometimes difficult to fully measure.

Mainstream music

Not so long ago, a record like NWA’s “Straight Outta Compton” was seen as such a threat to decency and public safety that the FBI felt compelled to intervene. Now, one can watch Gwyneth Paltrow reciting Ice Cube’s “Gangsta Gangsta” verses on British TV with fellow Oscar-winner Geoffrey Rush beatboxing beside her. Adele can take a coinage from the same song’s lyrics (which in context refers to a Burgessian gang outing) and twist it into the title of “Rolling in the Deep.” The profundity of this cultural shift is hard to overstate.

Ice Cube, of course, is currently busy exec producing his slate of kid-friendly TV shows and films, joining a plethora of his peers to have entered into polite, mainstream society no worse for wear. “Cop Killer” author Ice-T is perhaps now better known for playing TV detectives; Dre’s success as a home electronics entrepreneur has come to rival his earnings from music; and onetime Brooklyn crack dealer Jay-Z can now be photographed mingling with Bruce Springsteen and Barack Obama.

Nor are these rappers being replaced with like figures. New traditionalists like Roc Marciano and Freddie Gibbs do peddle vintage slabs of gangsta rap to a devoted audience only slightly larger than that for modern jazz or bluegrass, but on Billboard’s last few year-end rap charts, the highest spots have gone to such figures as a half-Jewish former teen soap star from Canada (Drake), an art school-trained soon-to-be “American Idol” judge (Nicki Minaj) and an over-sensitive, fashion-obsessed gadfly (Kanye West), all of whom make music about as threatening as a glass of warm milk. Even anarchic L.A. collective Odd Future’s desperate attempts to up the outrage ante with lurid tales of rape and murder attracted less genuine condemnation than beard-stroking essays from music critics and an indulgent, “been-there-heard-that” shrug from the rest of the populace. Perhaps this is part of a gradual coarsening of the culture, but more likely it’s that the rest of the culture has simply caught up.

In the early ’90s, few of rap’s core critics seemed to have taken the time to really grapple with the music. Despite undercurrents of menace, the vast majority of hit rap songs have always concerned the same topics as hit rock or pop songs: dancing, getting wasted and getting laid. And even when the subject turned to violence, the distinctions between the various types of violence, and the rappers’ attitudes toward it, were enormously varied. Some violent images were meant to be offensive and threatening, but just as many were meant to be sad, or funny, or fictional, or often wholly rhetorical — the logical evolution of battle-rapping into the language of actual battle.

As Ice-T once put it: “Rap is really funny. But if you don’t see that it’s funny, it will scare the shit out of you.”

Rap’s fantastical reach

But even as the gangsta tradition settles into respectability, some of its pet fantasies have spread into ever more distant corners of the music world, with rap-inspired violent imagery popping up in the most unlikely places to sometimes jarring effect.

Last year, Rihanna’s “Man Down” video culminated with images of the singer shooting a man in the head. Britney Spears’ “Criminal” video saw the former Mouseketeer holding up a liquor store at gunpoint and carjacking a middle-aged woman. Katy Perry branded an assault weapon in the video for “Part of Me.” The opening medley of Madonna’s ongoing tour ends with a choreographed slaughter set to the tune “Gang Bang,” in which the singer dispatches a bevy of (mostly black) dancers as gunshot sound effects ring out and blood splatters across the three-story LCD screens behind her. At the close of the tune, she chases one last wounded assailant to the foot of the stage. He pleads for his life, Madge mimes executing him, kicks at his corpse and steals his gold chain. The routine’s numerous aesthetic borrowings from early ’90s hip-hop can’t have been accidental.

Gangsta rap did not emerge out of a vacuum. Thanks to the viral spread of crack cocaine and the nihilism that went with it, coupled with systemic urban neglect and aggressive policing, the 1980s were an appalling period in which to be poor and black in a large American city. Proto-gangsta rap singles like Toddy Tee’s “The Batteram” and BDP’s “9mm Goes Bang” were simple first-person narratives describing this sorry state of affairs, and they resonated within their communities. Gradually, this tradition would transform into the source of some of the most popular and profitable pop music in the country, and eventually bequeath our culture with a set of tropes and images that can now be appropriated as theater for a Madonna performance. How we feel about this deserves some real thought.

Art has its consolations, but they can be dangerous when employed to assuage a guilty cultural conscience. The near-genocide of the American Indian in the 19th century, for example, gradually became the “taming of the West,” its brutal battles recast as escapist children’s tales of cowboys and Indians. Now, the period of American history in which governmental failure left poor urban minorities to kill each other for the privilege to sell drugs to their neighbors has given us the folk hero of the Tec-toting gangster.

That’s a legacy that we’ll have to live with, softened by the consolation that the period at least produced such records as Nas’ “Illmatic,” Mobb Deep’s “The Infamous” or 2Pac’s “Me Against the World” — complex works of pulp art as brutally beautiful as any Sam Peckinpah film or Cormac McCarthy novel.

More recently, however, the period has also produced Kendrick Lamar, a Compton native whose major label debut, “good kid, m.A.A.d. city” topped a number of 2012 critics lists. Just a year old when “Straight Outta Compton” hit the streets, Lamar is perhaps the first commercially significant rapper to make contextualizing the post-gangsta landscape his primary artistic concern, as he describes firsthand the sad, solemn cityscapes with a “Pakistan on every porch” and “bodies on top of bodies,” where not having a gang affiliation can be just as dangerous as having the wrong one.

Yet underneath it all is the sense that all this ugliness is an inheritance; the legacy of an older, more tragic generation there to be acknowledged and eventually transcended, with Lamar holding out hope that “the next generation maybe can sleep/with dreams of being a lawyer or a doctor/instead of the boy with the chopper.”

Gangsta rap has become an indelible part of our culture — it no longer requires a pro or con stance, it’s something that’s simply there. But the tradition is hardly set in stone, and a greater dose of Lamar’s hard optimism, with its emphasis on generational progress rather than simple personal advancement, would be a welcome addition.