Music: Pop - She's almost soulful. Really

Whitney Houston Sheffield Arena Gang Starr Astoria, London
Houston, she had a problem. A record company press officer said that the stage lighting was on the blink; the star said later that there was a "technical difficulty" with her voice. Whatever the reason, Whitney Houston's first UK concert for five years started 50 minutes late. Just to add insult to injury, she made up for lost time by dropping two of her songs, but she kept in the two that were sung by her brother, Gary, and her backing vocalists. The fans decamped to the bar. The woman they had paid pounds 40 to see wasn't on stage herself for much more than an hour.

It feels odd, then, to pronounce the concert a triumph, but that's what it must have been if I, a Houstosceptic, was won over. When the show eventually started, all my prejudices seemed about to be vindicated. "Get It Back" was a grim little r'n'b shuffle, hardly aided by Houston's four dancers, who had decided, for reasons of their own, to skip around holding violins and wearing Venetian masks. The diva, meanwhile, strutted imperiously in a floor-sweeping, fake-fur pink Dolce & Gabbana coat. It was horrible.

But when Houston took off the coat the show took off. No longer having to worry about tripping, she turned in a relaxed, intimate performance, surprising us with sudden smiles and throaty laughs, and responding chattily to shouts from the audience. Unless she's a better actress than her films would lead you to believe, she was enjoying herself.

I was astounded. Personally, I'd always assumed that Houston was an android: her perfect physique designed by computer, her creamy skin moulded in plastic, a serial number concealed beneath her immobile hair. For all her beauty, she has exuded as much sex appeal as a Kenwood blender over the years - and considerably less emotion. But on Thursday, she seemed to have undergone a Pinocchio-like transformation into a human being. It may seem over-generous to fete an entertainer for the casualness with which she taps her foot or leans on the piano, but in the world of lip- wobbling power-balladeers, such spontaneity is as unexpected as a potential Tory prime minister coming out of the closet. At a Celine Dion concert, say, every tilt of her head looks rehearsed. Houston, in contrast, wisely leaves the choreographed movements to the dancers. While they rushed through routines that belonged somewhere between a lapdancing club and an aerobics class, their boss upstaged them with a flirt and a joke.

Her young band, too, seemed to be flesh and blood rather than the session robots I'd expected. Fast, funky percussion gave "My Love Is Your Love" a kick it lacks on the record. Boogie-woogie piano did the same for "I Go To The Rock" and a tricky guitar solo for "How Will I Know". Even the dreaded "I Will Always Love You" was almost understated, with Houston accompanied by an acoustic guitar and a piano.

"Oh Lord, it takes a lot of breath to sing that song" she cracked afterwards. The remarkable point was that she did indeed sing it, instead of just using it to demonstrate her larynx's acrobatics. Maybe her new respect for a tune - and the new raspiness to her voice - can be credited to the evening's "technical difficulty". If so, she should have one more often.

Recently, the multi-millionairess has tried to reinvent herself as a streetwise girl-in-the- hood. She is miscast: Houston is no Lauryn Hill, even if she was apparently on her way to a Lauryn Hill fancy-dress party in the "My Love Is Your Love" video. On Thursday, though, it seemed as if a much more dramatic transformation might be in the offing. One day soon, Houston may no longer be just a vocal technician. She could be a soul singer.

Gang Starr have probably sold fewer records in a decade than Whitney Houston sells in a week, but Full Clip, the revered New York duo's 10th anniversary retrospective, is still a unique achievement. Few hip-hop acts have kept going for a dec ade. And almost none of them has put out five consistent albums, each one free of Bee Gees samples, along the way.

Gang Starr make raw, grassroots hip-hop, but strive for innovation within their self-imposed boundaries. Christopher "Premier" Martin's production is always musical, often moving at a strolling pace and incorporating finger-clicking brass and double bass from his jazz record collection. Keith "Guru" Elam's lyrics stand well back from the violent, misogynist, paranoid fantasies of his peers. Instead he tells moral, intelligent stories, even when chronicling the same world as the Uzi-and-Ho brigade. Gang Starr's name may be two Rs away from gangsta, and Full Clip may be firearm jargon, but "Tonz `O' Gunz" and "All 4 Tha Ca$h", for instance, possess a seriousness that should have most gangsta rappers shuffling their Adidas sneakers in shame. As Guru says on "Discipline", "Instead of preaching death in my songs, I breathe life."

This brings us to another matter: on a Gang Starr record, every word is easy to make out. This, too, is a pretty rare achievement ... and one which made the Gang show on Wednesday all the more disappointing. It reminded me why I don't review many hip-hop concerts. Quite apart from the Astoria's having been turned into a sauna for the occasion, both the rapping and the backing were a distorted, thudding racket. Surely there is a problem in a medium built on words if every one of them is incomprehensible.

Nor was there much in the way of visual compensation. Guru's showmanship begins and ends at his tossing a microphone from hand to hand as he and three of his mates pad around a bare stage. Bearing in mind the number of times Guru informs us that he and his Premier are "kings of the underground", I suppose the primitive show was his way of being true to the street. That's no excuse. The Astoria isn't a street, it's a concert venue.

Whitney Houston: Birmingham NEC, tonight; Wembley Arena, Wed, Thurs & Sat. Ticket hotline: 0870 444 4040