"Don't call it a comeback!" LL Cool J bellowed famously on "Mama Said Knock You Out," a song that, in spite of Cool J's demand, ranks as possibly the greatest comeback song of all time. That hip-hop quotable has been reiterated, paraphrased, and co-opted time and again, in part because it speaks directly to rappers' fear that for most fans, out of sight means out of mind. Of course, when Cool J released the song, he was far from finished, but his anxiety about being labeled a has-been registered as strongly as the visceral, pounding production of Marley Marl. One of hip-hop's first superstar producers, Marl helped develop sampling as an art form, through his pioneering work as the beat savant behind Juice Crew. The legendary producer began the '90s strongly with his career-revitalizing production on Mama Said Knock You Out, but sat on the sidelines for years as sonic progeny like Pete Rock, DJ Premier, and Jay Dee racked up production gigs, respect, and big paydays. As its title suggests, Re-Entry marks a comeback of sorts for Marl, albeit an unusually quiet one. The fourth entry in BBE's Beat Generation series, Re-Entry finds Marl manning the boards for a roster that includes a single Juice Crew holdover (Big Daddy Kane), the odd cult favorite (Pete Rock's gifted younger brother Grap Luva), and a slew of newcomers. In typical Beat Generation style, the beats on Re-Entry consistently outshine the rhymes. But while the rapping seldom threatens to bring back memories of Juice Crew's heavy hitters, Marl's masterful production—a deceptively artful combination of jazzy sophistication and head-nodding old school boom-bap—carries the disc's weight with ease. Like Marley Marl, Brand Nubian showstopper Grand Puba has a reputation that precedes him. He provided a charismatic comic counterbalance to Brand Nubian's often-strident identity politics, but his solo career never took off for all his prominent ghostwriting work and spirited guest turns. Understand This, Grand Puba's first album for Koch, tries to establish Puba's credibility as a solo artist, but accomplishes exactly the opposite. Shrill and inane, the record inexplicably attempts to remake the noted Five-Percenter as a jiggy, party-hearty playboy, with disastrous results. Clumsily loaded with absurd song concepts and simplistic, self-produced beats, Understand This doesn't even work on a purely commercial level, except for "What's Up Wit It?" and "Up And Down," a pair of dance songs as catchy as they are shallow. If Understand This were the debut of an up-and-coming rapper, it would merely be a bad album from an artist without much to say. Coming from an artist of Puba's stature and talent, it's a dispiriting fall from grace.