Al Jarreau, Hammersmith Apollo, London

A jazz singer on the sly

Al Jarreau loves jazz. In fact, he's really mad about jazz. He keeps it quiet, though, like it's his guilty secret. And those who know the singer only through his albums, especially from the Eighties onward, would probably not be aware of his love for the music he started with, and to which he now only returns in concert. Why does he do it? He's quite open about the fact that the high-production, low-interest soul with which he fills his albums is what gets airplay in America. Sadly, it's just the kind of obvious wallpaper preferred by this country's Jazz FM, a station notorious for playing virtually no real jazz.

But Jarreau live – now that's something else. Even on his mainstream hits, such as "We're in this Love Together" or "Mornin'", his extraordinary vocal palette elevates the rather ordinary material to a more exciting plane. Jarreau doesn't just sing a melody. He moves between squeezed percussive plosions, a wide-open operatic tone, querulous trails, and close-miked imitations of a plucked bass, all driven by a round-edged jerkiness that keeps his body moving, restless, like an electric wirebrush come to life.

That's not all Jarreau can do. When he performs "Your Song" (the Elton John number brought a roar from the crowd – Jarreau first played it in 1976, and it's been a favourite ever since), he holds a long note over the vamps in between verses. The ability he has to tangle, mangle and take this note to places it's never been, and might well not want to visit, is utterly distinctive. Other singers, such as Michael Franks, pepper their work with jazz references. But Jarreau uses his voice as an instrument, just as capable of taking a solo as his saxophonist, and that's what marks him out as a proper jazz singer even when the material itself does not belong to that category.

There were one or two tantalising moments when Jarreau did go back to his roots. There was a slow version of "How High the Moon", a brief bebop duet taken at breakneck speed with the sax, and the backing band played a few bars from Horace Silver's "Sister Sadie". Ah, we sigh, if only Jarreau would play a residency at a small club.

Alas, he prefers big venues, big synthesiser and percussion-loaded bands, and the big money that accompanies all that. His jazz audience always goes away on a sugar high, with a nagging need in the stomach for something a little more savoury. But after a tour-de-force encore of Chick Corea's "Spain", Jarreau managed what performers are always told to do – he left 'em wanting more.