What if bebop ruled the world and jazz-pop went to hell?

The London Jazz Festival closes tonight with the America-based vocalist and bass player Richard Bona supporting Britain's Jamie Cullum, an order which on the grounds of technique and respect ought to be reversed. Earlier in the week, however, a local star, Soweto Kinch, opened for the US's David Sanborn and left the million-selling alto saxophonist looking as if he needed to take a few lessons.

Kinch's quintet started with a rap, "Opening it up", Kinch sharing vocals with his excellent trumpeter Abram Wilson (who sadly confined himself to singing and rapping for the whole set). The use of this street idiom is no gimmick; hip-hop rhythms alternate naturally with an uncompromising swing in this group, for the styles are both a genuine expression of Kinch's own experience. It is not even really a fusion - it is too organic to merit that label. Supported by single lines and spare chords from David Okumu on guitar, Tom Herbert's solid bass and Tom Skinner's drums, just nicely underamplified so that he could kick in without drowning everyone else out, Kinch's alto overflowed with ideas, urgently, passionately. His rap "What if bebop ruled the world? (On a jazz planet)" sets a serious but humorous message, in an acceptible form, about the lack of honour accorded to jazz musicians, and although Kinch is young he has the confidence to reach out and grab the audience by the earlobes to make sure they're listening. On the sax, too, he is forging a new voice, with a lovely breathy edge to his alto on one ballad, then raw and unplaned when showcasing his impressive technique.

After something so authentic and exhilarating, the contrast when David Sanborn came on was unbearable. Sanborn's chops are not disputed, although his musical taste (he has an unfortunate addiction to dull, cheesy jazz-pop) has always been a matter of heated debate. He can play well, but this was an occasion when the buttons marked "originality", "interest" and "discrimination" were switched to "off". Formulaic, super-competent solos came from guitar and keyboards, touching all the bases and failing to connect with any of them, while Sanborn produced paint-stripping high notes, his much imitated alto shorn of its normal gorgeous coat and sounding harsh and unlovely instead. I almost walked out after the first two numbers, already convinced that this was quite the worst concert I'd been to, possibly ever, but there was something fascinatingly awful about the keyboard sounds Ricky Peterson brought forth from his array of decks. Pointless pyrotechnics were filtered through pan pipe sounds not heard since the Eighties, while he opened Joni Mitchell's "Man from Mars" with an echoey piano synth that even Lionel Richie would be embarrassed to employ.

Earlier in the festival Bobby McFerrin showed that you can be around for 20 years and still have something to say. Taking his inspiration from his last album, which delved into tribal rhythms, he taught a scratch choir to assemble four- or five-part riffs over which he demonstrated his amazing vocal technique, slapping his chest and moving from a deep bass to the breathiest falsetto. He revisited past successes, getting the audience to sing Gounod's "Ave Maria" to which he provided a background of Bach's Prelude No 1 in C major, and performed three spontaneous improvisations with a couple of guests, the dancer Sharon Wray and the trumpeter Byron Wallen.

McFerrin ended with a tour de force encore in which he went through all the songs and much of the dialogue of The Wizard of Oz in 10 minutes flat. In such a concert, the question "is it jazz?" really didn't seem to matter.

The London Jazz Festival ends today. For details of final performances visit www.serious.org.uk/rgjazzfest.shtml