Mary J. Blige and Jay-Z seamless

R & B singers and rappers are musical codependents. The former sing the hooks that stick in your head, the latter serve up the urban street cred that's an essential hip-hop selling point.

And Mary J. Blige and Jay-Z have needed each other from the get-go. As far back as 1996, she sang the chorus on "Can't Knock The Hustle," the very first song on his now-revered first album, Reasonable Doubt.

So it's a wonder that the two leaders in their respective fields have taken this long to embark on the collaborative "Heart of the City" tour that brought them to the Wachovia Center on Sunday for a seamless two and a half hour show packed with hits from both sides of the hip-hop soul coin.

The evening kicked off with "Hustle," with Jay-Z making his more-subtle-than-most cheesesteak reference ("I got more at stake than Philly"), and the two marquee names sharing the stage with a sharp, versatile band that swelled to 21 strong for Blige's portion of the show, including a four-piece horn section and seven-member string ensemble.

Jay-Z exited after "Hustle," leaving Blige to detail her ultimately triumphant struggles with self esteem and philandering paramours on songs like "Not Gon' Cry" and "No More Drama."

In high heeled boots, a glittering jacket and Frisbee sized hoop earrings, Blige sang everything with emphatic conviction, all night long. She's been known as the Queen of Hip-Hop Soul since she debuted with What's The 411 in 1992, but in many ways Blige is a throwback to an earlier style of R & B that focused on everyday romantic strife.

And her singing isn't marked by the rococo flourishes of competitors like Mariah Carey and (Jay-Z sweetheart) Beyonce. In comparison, it can seem blunt and hard edged. When Mary J. gets down to the business of bonding with her empathetic audience, there's no room for excessive vocal decoration. And she can be even more direct in her spoken interludes: At one point on Sunday, she excoriated deadbeat Dads: "I want to know what makes a man walk away from a child, and say 'That kid is not mine'?" she asked, before repeatedly singing the line "Why would you deny yourself?" with growing intensity.

In low slung jeans and shades, Jay-Z - real name: Shawn Carter - followed Blige's emotional catharsis with a display of smooth talking bravado that was no less impressive. "I got a million of these records," the self-proclaimed "best rapper alive" announced after the Jackson 5 powered "Izzo (H.O.V.A.)." And as the old-school thunder of "99 Problems" percolating bounce of "Can I Get A . . .?" and the horn happy celebration "Roc Boys (And The Winner Is. . ..)" were all delivered with panache and a surfeit of self-confidence, he didn't seem to be exaggerating.

(On the latter tune, from last fall's American Gangster album, Jigga announces that "the Roc boys" - that is, his fellow rappers on his Roc-A-Fella records roster - "are in the building tonight." At the Wachovia, Roc boy Memphis Bleek was indeed in the house, but one key Jay-Z cohort was missing: Philadelphia rapper Beanie Sigel, who was sent back to jail on Friday for a parole violation.)

But if Beanie was never mentioned, Barack was. Jay-Z all but endorsed the Democratic candidate, after replacing a giant picture of a confused looking President Bush on the video screen with a more flattering shot of Obama. "When will they learn?" he rapped. "Only love kills war." He then made it clear that he was not speaking as an Obama surrogate but as a "free American citizen," and asked: "Y'all ready for change, right?"

Thanks to the efforts of the unsung - and un-introduced - band, the show avoided any sustained breaks in rhythm.

Jay-Z briefly killed the momentum of his set, however, when he teased the audience with intros to several of his hits, then failed to play them.

The evening got back on track, though, with audience members only too happy to do the rapping for him on "Big Pimpin'." And the show went out in style with "Heart of the City (Ain't No Love)," in which Jay Z rhymed in tribute to a scrambling Philadelphia Eagles quarterback - Cunningham, not McNabb - and Blige sang with gusto the hook originally delivered by Bobby "Blue" Bland.