The foreboding, faraway skree announcing Mobb Deep's "Shook Ones Pt. II" is one of rap's most perfect sounds—but what is it? It might be a horn. But it also might be an exploding steam pipe, or a car alarm, or a laser-jet printer. An even stranger sound follows it: four notes played on either a guitar imitating a piano or a piano imitating a guitar. The line is so disorienting that it inspired a sixteen-year long hunt for its source, which only ended in 2011 when producer Havoc confessed that sample snitches had finally pinpointed their target – a three-second piece of a Herbie Hancock instrumental, sped up and then slowed down. Playing the sample back to back with its source does absolutely nothing to resolve the mystery of "Shook Ones Pt II."

For the kids who made it—Albert "Prodigy" Johnson, from Hempstead, and Kejuan "Havoc" Muchita, from Queensbridge—"Shook Ones Pt. II" was half war cry, half last gasp. It announced The Infamous, Mobb Deep's second album and their first classic, and in the canon of career-revitalizing rap singles—Kool Moe Dee's "How Ya Like Me Now", LL Cool J's "Mama Said Knock You Out", Dre's "Still D.R.E."—"Shook Ones Pt. II" is maybe the most effective, and certainly the most devastating. The song was a rebirth, and the album that it foreshadowed would rewrite their legacy entirely.

The Infamous was not supposed to happen. Johnson and Muchita had already gotten their shot, releasing a corny, forgettable debut called Juvenile Hell in 1993 that sold 20,000 copies before being dwarfed by Illmatic, which had already traveled the world as a demo before its official release in April of '94. At every radio interview, Havoc and P found themselves answering questions about Havoc's Queensbridge neighbor Nas. In his 2011 memoir My Infamous Life, Prodigy recalls "Halftime" pumping out of the speakers at what was supposed to be a Mobb Deep in-store in D.C. Shortly afterward, Mobb Deep were dropped from their label.

They retreated, licking their wounds, to Havoc's mother's house. In New York, things were getting increasingly serious–Enter the Wu-Tang (36 Chambers), also released in '93, had already shipped platinum by May of '94. A revolution was brewing in their own city, and the authors of puerile kiddie sex raps like "Hit it From the Back" were in danger of getting left behind forever. It was out of this brew of desperation and determination that The Infamous began to take shape. Their music took on a grimmer, darker tone.

A few key people took notice. One was Schott Free, an A&R at Loud Records and former member of the short-lived rap group Legion of D.U.M.E.; another was Matteo "Matty C" Capoluongo, who ran The Source's News section and wrote its venerated Unsigned Hype column. Capoluongo and Free occasionally worked together on behalf raw, roughneck rap, the kind of stuff the industry required occasional nudging to embrace. It was Jacobs, for instance, who initially brought Wu-Tang's "Protect Ya Neck" into The Source offices. He and Matty C slipped Mobb Deep's new single, the fierce and focused "Patty Shop", to influential DJs Stretch and Bobbito. Word spread, albeit faintly, that the duo might yet have new life in them.

The third important figure behind The Infamous is Q-Tip, whose bemused presence floats over Mobb Deep's early career. When they were still teenagers hungry for a record deal, Havoc and Prodigy accosted Tip outside of the Def Jam offices. He obligingly ushered the duo into the hallowed offices of Lyor Cohen, whereupon they rewarded him by accidentally shooting a Def Jam employee in the stomach. He didn't give up on them, however, and on The Infamous, he does enough work to qualify as a temporary third member—co-producing and rapping on two songs ("Give Up The Goods" and "Drink Away The Pain") and working with Havoc to refine and perfect the album's indelible atmosphere.

It is that atmosphere that lingers, untouched and intact, now that Havoc and Prodigy are reissuing the album via a PledgeMusic-funded project. In addition to the original album, they are including a disc of rare and unreleased tracks from the sessions along with a full new album, confusingly, also called The Infamous Mobb Deep. The branding is odd, and the timing for the project feels a little off: For one, they are claiming a 20th-anniversary celebration for The Infamous a full year ahead of schedule. For another, the duo recently suffered through a highly publicized, and extremely ugly, split while Prodigy was in prison. Maybe the reissue functions as a renewal of the vows between the two, a way to patch up relations while reminding rap fans, and themselves, of the potential power of a flagging, listless brand.

The reissue, if nothing else, is a helpful reminder that this power is still there, for whoever wants it. The reason The Infamous remains so untouchable today goes beyond its individual qualities —the vividness of Prodigy's imagery, or the richness of the Queensbridge slang they introduced —into more rarefied air. With The Infamous, Mobb Deep invented a feeling, one that was more important than any individual word, chorus, or rhyme. All of New York was embracing degraded production at the time, but Havoc pushed beyond the low-resolution samples of RZA's Enter the Wu-Tang (36 Chambers) into near-total abstraction, producing a masterpiece of low, muffled, and malevolent sounds. The stand-up bass sample on "Trife Life" sounds like it has cotton balls behind the strings. The implication of vinyl crackle in "Eye for An Eye" feels like a needle dragging on tendons. "Q.U. -- Hectic," boasts a glowing, pulsing piano echo that feels nearly sentient, like some kind of slit-eyed pet monster Havoc is resting one hand on to keep calm.

Throughout, Havoc and Prodigy exude the confidence and comfort of artists who have found their voice and their ideal environment, and can break whatever rules they want. If they want to interrupt their album after one song in so Prodigy can deliver an Henny-soaked rant promising to punch other rappers in the face "just for living?" They'll do that ("The Infamous Prelude"). If Q-Tip wants to drop into "Drink Away The Pain," a tightly themed song about alcoholism, to rap only about his clothes—he'll do that. Nothing disturbs the surface. Every decision feels seamless and inevitable within the bubble Havoc and P. created.

There is a wholeness, an impenetrable circularity, to The Infamous as a result. Havoc, who grew up in Queensbridge, taught Prodigy how to rap in the secret-handshake style of his projects, while Prodigy, whose grandparents were jazz royalty, taught Havoc how to use studio equipment. In each case, the student became more adept than the teacher, and the result is a seamless cohesion, Havoc and Prodigy representing two halves of an endlessly repeating thought. Sounds repeat themselves like distant lights, or recurring nightmares, blurring your sense of the album's progression: That unforgettable "skree" from "Shook Ones" reappears on the chorus of "Q.U. – Hectic." With apologies to Nic Pizzolatto, there is a distinct "This has all happened before, and will happen again" air of fatalism to The Infamous. And while gangsta rap had been fatalistic before 1995, it had never sounded quite this fatalistic.

Appropriately, The Infamous also marked the moment that the language in gangsta rap shifted from corner scrambles and specific vendettas to all-out war, endless and impersonal. "Every angle of the car was smoked out and tinted/ So we couldn't tell if the enemy was in it," Prodigy raps on "Trife Life". He's not targeting anyone in particular--just "the enemy." This was the logical conclusion to the lyrical (and literal) arms race in mid-90s gangsta rap; Mobb Deep got all the way to the end first, and said everything best. The album's most famous and oft-quoted lyrics remain "There's a war going on outside no man is safe from," from "Survival of the Fittest", but Havoc's "Q.U.--Hectic" line "Real like an innocent child that turned killer" tells it just as well: From here on out, this would the only kind of reality Havoc and P would explore, or acknowledge.

That worldview is what's missing on The Infamous Mobb Deep. Or, if it’s there, it comes through crackly and unreliable, like a radio station just out of range. As a Mobb Deep project, it's mortifyingly weak—before 2006's Blood Money, the duo had never made a bad album, and Blood Money was bad precisely because it wasn't a proper Mobb Deep album, but rather a fourth-rate G-Unit record with Havoc and Prodigy rapping listlessly on it. This time, they have no one to blame but themselves. Their lack of investment is audible on every level: The beats feels tinny and wheezy, and the album hardly sounds mastered, full of clippy snares and poorly synced vocals. The beat on "Get Down" is barely audible. The hooks are just flat chants with no rhythm or life in them.

The chemistry between the two, more troublingly, is nowhere in sight. Prodigy has receded further and further into idiosyncrasy as a solo artist, to the point where it's difficult to imagine him belonging to a group at all. He doesn't even offer any of his choice "HOW I FOLD MY BANDANA" weirdness: "I flood the cold streets with your hot blood", from "Taking You Off Here", is about as hard as he tries, as far as imagery or wordplay or contrast goes. He can still summon vivid, bone-chilling imagery, and was doing so as recently as his Bumpy Johnson EP. But he barely shrugs his way through The Infamous Mobb Deep. Taken as a whole, the album is exactly the sort of hastily tossed-off, forgettable project that legacy acts will sometimes tack onto can't-miss releases such as this. It's a shame they did.

The disc of rare and unreleased tracks from the 1994 The Infamous sessions, on the other hand, is exactly the sort of thing that reissues are made for. Many of these songs have been available to hardcore rap fans for years, but the best of them, like “Take It In Blood” and “Gimme The Goods”, are the equal of anything that made The Infamous. They extend the album’s long shadow and give a fuller picture of Mobb’s startling leap in confidence from Juvenile Hell to Infamous. There are a couple fan Easter Eggs here too, the most notable of which is the “lost reel” early version of their Raekwon/Nas collaboration "Eye For An Eye" with an alternate Nas verse and a vintage Ghost verse. But my favorite moment might be the mind-bending live freestyle session between Mobb Deep, Raekwon, and Nas. Rae spits a verse that would end up on “Incarcerated Scarfaces”; Nas follows up. Both of them, however, quiet down when Havoc and P start rapping. The duo are still in complete, blissful sync, their voices young but old-sounding, their newfound chemistry a thing to behold. Apart from murmuring some appreciative noises, Rae and Nas are reverently silent. You realize, with some amazement, that they just feel lucky to be in the room.