Sometimes it is not only hard to separate the artist from the hit - it's hard to forgive them for it. So it is with Don't Worry Be Happy and Bobby McFerrin, one of the star attractions of this year's Arts Festival. One reason for this, no doubt, is the fatuous sentiment of the lyric. Another is the infuriating catchiness of the tune. And an overwhelming third is the blighted memory of what seems like most of 1988 when it was impossible to go out, anywhere, without hearing the damn thing on somebody's radio. In McFerrin's case, however, one has to make a special effort to forgive and forget because of the truly revolutionary contribution he has made to the art of the jazz vocalist. Many singers are given to talking about their voices as 'instruments', but McFerrin's is a whole band's worth, as he has proven time and again with his extraordinary solo performances. The first time I heard him - or, at any rate, came to realise that I'd heard him - was on the soundtrack for Bertrand Tavernier's Round Midnight. I searched the credits in vain for the trumpet player responsible for a particularly lovely muted solo, and assumed that the reference to 'Bobby McFerrin, vocal' was a misprint. It wasn't, of course, and, if you listen carefully, the tell-tale sign that McFerrin's voice isn't the real thing is that most trumpet players with a mute stuck in the bell of their horns don't sound anything like this good. McFerrin started his career as a pianist, and could easily have gone the Nat King Cole route as so many others with both vocal and keyboard skills have done. It seems, however, that such a conventional approach was not enough of a challenge for him, so he took to appearing in concert solo with nothing to support his voice, rhythmic breathing and percussive chest beating but a microphone. He has said that each concert is a blank slate, and names Keith Jarrett's solo improvisations as the example of high-flying performance without a safety net that inspired him. There isn't much doubt that a performance of this kind is extremely difficult to do, as you can tell from the dearth of Bobby McFerrin imitators. In common with guitarist Stanley Jordan - who, at around the same time, developed a fretboard tapping technique that allowed him to play the guitar almost like a keyboard instrument - he was an obviously important innovator, but far too much like hard work to copy. It is also probably fair to say that for both men virtuosity ultimately triumphed over subtlety of expression. Each was profoundly impressive to witness in performance, but not, generally speaking, particularly moving to listen to. It is hard to fault McFerrin for exploratory zeal, however. He and his extraordinary vocal technique have been heard in partnership with Yo Yo Ma, Wayne Shorter - who is also appearing at this year's festival - vocalese master Jon Hendricks, Manhattan Transfer, Herbie Hancock, Chick Corea and many others, including the Muppets. At the height of his singing career he decided to study classical conducting and has gone on to enjoy some success in that field, as well, particularly with the St Paul Chamber Orchestra, of which he is also creative director. It is not unusual for musicians to pride themselves on being unrestricted by boundaries, but McFerrin has taken that rather further up the road than most, as the list of guest artists for his Hong Kong concerts shows. On the first night, February 9, he will be sharing the vocal duties with canto-pop star Eason Chan, singer percussionist Jun Kung and a primary school choir, augmented by an erhu player. On the second, February 10, Eugene Pao will be adding some guitar licks, while another local pop luminary, Cass Phang, will also be singing. McFerrin's current recording contract has him simultaneously signed to a jazz and classical label, but his pop and world music interests also continue to crop up on his recordings. He is most certainly not an easy man to pin down. It is possible to argue, as tends to be the case with artists of remorselessly eclectic bent, that McFerrin spreads himself too thin. For all the range and virtuosity of his work, in recent years I haven't heard anything from him that truly struck me as being as good as that wonderful Round Midnight solo, or his equally magnificent contribution to Jon Hendricks's vocalese version of Miles Davis's classic Freddie Freeloader, on which he sings the Wynton Kelly piano part quite wonderfully. On the other hand what would I know? His ghastly novelty tune hit No.1 on the pop charts in just about every country that bothers to maintain one. Don't worry. He's happy.