One Of The Great Divides among musicians falls between those who can fill the Festival Hall with a solo recital and those who can't; and "filling" for these purposes is a matter of projecting personality, as well as of luring bottoms on to seats.

Last Tuesday Maxim Vengerov did both, pretty convincingly. And though it wasn't the most pyrotechnic show of strength I've seen him give, it told you loud and clear why this mere 23-year-old is now the hottest talent in the string world. In the seven years since his international career began, with a first prize in the Carl Flesch competition at the tender age of 16, he has grown into the sort of confidence that earthquakes couldn't shatter. To stand naked (as it were) on the Festival Hall stage and draw an audience of several thousand into something that purports to be chamber music is no small thing. But Vengerov can do it. And if he does it more comfortably in some repertory than others, well, that's not too terrible a failing.

His Mozart (the E Minor Sonata K304) was limited: a showman holding back in the interests of style and as a result not giving enough. His Beethoven (the Kreutzer Sonata) sacrificed tone to technique and delivered a set of variations in the middle movement that could have done with more variety. But in the Brahms D Minor Sonata he was on secure ground, matching fire with finish. And the Hungarian Dances that followed were a Technicolor outrage of affirmative good humour, swagger, cheek. Of course, you have to ask yourself if it isn't all too much. The swank can be oppressive, and there are times when his posture is so arched, the violin pointing to the sky, that you wonder (a) how he sustains any bow-weight and (b) how he manages not to fall flat on his back. But the circus routines come with an ironic playfulness that checks their growth-potential for vulgarity. And then there's the matter of musicianship, which in Vengerov's case surpasses that of any other younger-generation fiddler I can think of - including Ann-Sofie Mutter, whose Barbican performance of the Sibelius Concerto was the one questionable contribution to Sir Colin Davis's superb Sibelius cycle with the LSO.

It came between performances of the 6th and 7th Symphonies that were slow but somehow right, and magisterial demonstrations of the work Davis has put into enhancing the LSO string sound. The Concerto, though, raised issues between soloist and conductor as to how slow (or fast, or both) you can get without a doctor's certificate. And Mutter, to be blunt, went off the rails - with the wilful eccentricity and wayward intonation that seems to have usurped her old, learned-at-the-feet-of Karajan patrician ways on recent discs. It wasn't comfortable. But if you like white-knuckle rides you got your money's worth. And for its sense of risk alone, the combination of terror and magnificence in Mutter's playing was memorable. Which is more than you could say for yet another star violinist passing through London this week, Vadim Repin.

Repin was here for the South Bank's Prokofiev Festival, devised by the LPO to sell the composer as someone of depth as well as dazzle and, in the process, dust down some forgotten works - including his first attempt at opera, Maddelena, which featured on Wednesday. A miniature Russian take on Grand Guignol, Maddelena is a single-acter for five voices and male chorus on the theme of destructive beauty, written when Prokofiev was barely out of his teens; its timing, circumstances, subject matter and ornate Romanticism (youthfully indulged) all bear curious comparison with Erich Korngold's Violanta, the short but sumptuous Venetian Renaissance shocker unearthed earlier this year by Opera North.

Violanta fulfils its promise of passionate excess, but Maddelena somehow doesn't. The gestures are big but heartless, controlled ultimately by acalculating hand. And like much of Prokofiev's later stage writing, it directs the weight of its creative interest not to the voices but to the accompaniment. In fairness I should add that Prokofiev completed only a fragment of the orchestration himself: our own Sir Edward Downes took on the task after Prokofiev's death. But the result suggests that this accompanimental bias ran deep in Prokofiev's psyche. Deep enough, at least, to be discernible from a piano score.

Vadim Repin's part in the concert came before the opera, in a Prokofiev 2nd Violin Concerto that I didn't care too much for either. Born, like Vengerov, in Novosibirsk and only slightly older, 26, Repin is in obvious rivalry with his compatriot; and his programme-book biography goes so far as to call him as "the foremost young violinist to have emerged from Russia since the days of Heifitz". Pistols have been drawn at dawn for less. In truth, Repin is a very different animal to Vengerov: a poet rather than a public orator, and without the absolute assurance that makes Vengerov's performances so strong. He played this concerto from the score (heaven knows why, when he's recorded the piece and must have played it live often enough). The tempi were switchback, in ways that came across as indecision rather than excitement. And there was no bite, no muscle to drive the rhythms - nor any help from the weakly capricious conducting of Gennadi Rozhdestvensky, who seemed indifferent to what he was doing and unconscious of its failure. I hate to be so negative about all this, because the Prokofiev Festival has been a good idea, well- executed and deserving of support. It's just that this was not its best face or its finest hour.

Chelsea Opera Group had a fine hour (or three) last weekend in a QEH concert performance of Jerusalem, the French opera Verdi adapted out of his Italian I Lombardi in an early, "galley years" attempt to woo Parisian audiences. It hasn't fared as well as the original - which is to say, it's never done - and received wisdom has long held that the original is better. But this uncommon chance to hear the piece suggested otherwise.

Why? Because Verdi's adaptation wasn't just a matter of accommodating a change of language and adding the obligatory Parisian ballet (omitted at the QEH), but a substantial rewrite that cleaned up a fatuous story of Crusading passions, preserved the best writing from the first version, and enhanced it with new material that drew on the intervening experience of scores like I Due Foscari and Macbeth. It also made the piece more practicable by reducing the requirement for principal tenors from one to two.

The Chelsea Opera tenor lead was Stuart Kale, who was a late replacement for someone else but did it beautifully, with nothing beyond a slight score-fixation to betray the fact that he had learned the role from scratch in four days. And there was a true discovery in Susan Stacey, who sang the soprano lead with a secure combination of coloratura brilliance, dramatic weight, and enough big, open top notes to brighten the lives of a few British opera managers I can think of. With accomplished contributions from Chelsea Opera's amateur orchestra and chorus and a conductor, Andrew Greenwood, who knew the idiom and how to make it work, it was a fine achievement. An example to us all. Lord Chadlington was rumoured to be in the audience, making notes; but it was probably his resignation speech in first draft.