THE CLOSER.

Chris (Ludacris) Bridges, the twenty-nine-year-old m.c. and actor, is perhaps best understood not in the context of other rappers but in that of a sports figure: the Yankees' closer Mariano Rivera. Nobody complains that Rivera doesn't pitch entire games--he can insure victory in an inning. Ludacris's best work is similar; in just six years, he has appeared on more than forty tracks by other artists, contributing sixteen-bar verses that are often clever and rowdy enough to make you forget everyone else on the song. As he puts it, in typically blunt fashion, on "Blow It Out" (from his 2003 album, "Chicken–N–Beer"), "All these rappers want to know what I'm getting for sixteen: try eighty. Want a discount? Blow it out your ass." Ludacris can erase three dull minutes in forty perfect seconds. (The skill applies equally to his acting: as a bilious carjacker in "Crash" and as a rapper in "Hustle & Flow," he proved that he doesn't need much time to make an impression.)

Usher's hugely popular 2004 single "Yeah!," about a trip to a dance club, features a classic cameo by Ludacris, in which he upstages his host and gets the girl--or at least brags that he will. Usher sings family-friendly lyrics about mingling with girls at the club. When one responds to his overtures, he hesitates in a gentlemanly fashion: "If I take that chance, just where's it gonna lead?" Ludacris, leering between Usher's Colgate smiles, seizes his chance: "Forget about game--I'm a spit the truth. I won't stop 'til I get 'em in they birthday suits." A former Atlanta radio personality, he expels his words with bracing oomph, confident as usual of his appeal and unembarrassed by his ribaldry. Here his lewdness makes Usher look innocent by comparison, a trick apparently worth eighty thousand dollars. (Ludacris may be selling himself too cheap. On his 2005 track "That's My Shit," he declares that "a song's worth a million once I lend my fucking voice to it." In the case of "Yeah!," which was the No. 1 song for twelve weeks, this might not be an exaggeration.)

This is not to say that Ludacris can't make an album; simply that the five he has made are not the measure of his talent. (This distinction is especially true for Ludacris, but it is becoming the rule for hip-hop. In the era of the mixtape, when dozens of songs appear each month only on semi-legal but widely distributed homemade CDs, major-label releases have become secondary texts, summarizing a year or two of an m.c.'s activity.) Ludacris provides dependable comic relief. His metaphors and double entendres ("stay on the track, hit the ground runnin', like Flo-Jo"; "money keeps flowin' like Niagara Falls") are comprehensible to any bright and corruptible ten-year-old. He is a fellow in filth to both contemporary standup comics and twentieth-century bluesmen, for whom a jelly roll is never just a pastry and a back-door man is never simply a repairman. But his booming voice and punch lines can be tedious over the length of an album, and what is vulgar and funny in one song can become offensive over twelve. When he appears on a track like Missy Elliott's 2001 single "One Minute Man," a brusque complaint about unsatisfying lovers, his cocksure patter is wish fulfillment for her aggressive sexual fantasies. ("Just cause I'm an all-nighter, shoot all fire, Ludacris: balance and rotate all tires.") When he's merely trying to fulfill himself, well, then it's a party of one.

Ludacris's new album, "Release Therapy," is, thankfully, a concise demonstration of his midnight-blue humor and bumptious oratory. The first single is called "Money Maker," and, like the blues singer Elmore James before him, Ludacris encourages women to shake their money-makers--that physical asset which "took your mama nine months to ...