Heat wave gets a bit hotter still

It was ladies’ night in the balcony at West Hollywood’s House of Blues. Orange T-shirted Clinique reps passed out samples of the perfume Happy to sextets of giddy party girls and best-friend-forever pairs out to see their favorite new singing heroine as the few fellows present faded into the background. On the dance floor, the crowd was more mixed -- definitively mixed, in fact, with both genders, most races and apparently all sexual persuasions sweating together as the DJ spun hits from Usher and Sean Paul. The room’s vibration was aggressively positive, well suited to Sunday’s appearance by Rihanna, pop’s latest polyglot sweetheart.

The 18-year-old Barbadian made a splash last year by turning a classic girl-group trope -- “Hey, Mr. DJ, play a song for me” -- into a reggae rave-up fresh enough to rule the summer. “Pon de Replay” opened Rihanna’s set on this second show of her first-ever headlining tour, and gave the impressively poised ingenue a chance to quickly take control of the willing crowd.

After some warm-up music from her gregarious DJ, Max Glazer, and a flashy little routine featuring four dancers, Rihanna strode onstage looking equine and a little stern as she undulated her white hot pants ensemble to the dancehall beat. Rhythm ruled for the first third of the show, as Rihanna and her crew moved to a groove that blended hip-hop and disco with Caribbean flavors.

Singing to Glazer’s well-spun backing tracks, Rihanna assertively proved that she wasn’t just a lip-syncer, showing off with agile vocal runs in between the familiar choruses. But this music was meant for dancing, blending West Coast hip-hop grooves and roots-reggae syncopation into Rihanna’s chrome-plated dancehall pop, and even her take on Dawn Penn’s vocally rich reggae classic “You Don’t Love Me (No No No)” sought to steam up the crowd more than make them pause and wonder at the young woman’s vocal gifts.

Then Rihanna reappeared in an equally sexy but more somber black outfit to perform her latest hit, the laborious ballad “Unfaithful.” Her reading of this philanderer’s plea for help had enough vocal acuity and dramatic verve to win “American Idol,” where undoubtedly it will soon become a standard. Rihanna thanked the crowd for making the song a hit on Black Entertainment Television’s “106 and Park” video show and the MTV equivalent, “Total Request Live.” With that comment, this daughter of Irish and Guyanese forebears firmly placed herself within pop’s proud tradition of informal desegregation.

The politics didn’t entirely stop there. After a few more dance-floor burners, Rihanna pulled out a stool -- pop’s universal sign for “stop enjoying yourself and pay attention” -- and invited the crowd to pay respects to the late Bob Marley through her rendition of his lovely, spare “Redemption Song.” Backed by only an acoustic guitar, Rihanna sounded serious enough to be singing the national anthem, and in a sense she was, so canonical is this Rastafarian prayer within the reggae community. The assertion of regional identity was as poignant, if as obvious, as a band of American Southerners playing “Freebird.”

Rihanna’s seriousness and raw virtuosity didn’t overshadow the alpha hotness that’s made her a pop queen, but it did lend a nice vulnerability that her own ballads sometimes lacked. Candid emotion always makes a performer more appealing, but Rihanna’s striking self-assurance, and the tight dance routines accompanying every song, didn’t allow for much self-revelation. Often compared to Beyonce (she was signed to the Def Jam label by that singer’s boyfriend, rapper-mogul Jay-Z), Rihanna doesn’t quite own the pure ambition of the woman with the guts to have fronted a group called Destiny’s Child, but she’s in the ballpark. Or, more appropriately, on the dance floor, with her ladies cheering her on.