Jazz HAROLD MELVIN AND THE BLUE NOTES The Green Room, Cafe Royal, London

Imagine, for a moment, being Harold Melvin. There you are, a soul singer plying an unknown, unrecognised and unspotted furrow for 16 years, when, in 1972, your home town of Philadelphia unexpectedly becomes the centre of black music. As a local who can sing, you and your vocal trio are picked up, promoted heavily, wonderful songs are written for you and you start to sell international quantities of records. At which point you discover it is not you the world is interested in. It is your lead singer, Teddy Pendergrass, the leather-clad soul God, the original Theopholus P Wildebeest who woos the ladies with his sensational tenor and his bedroom demeanour.

When Teddy leaves you to seek his fortune (and finds instead misery after being paralysed in a car crash) you tumble back into obscurity. Then, in the Eighties you watch as your songs are picked up by British soul boys who grew up on them and turned into significant earners ("Don't Leave Me This Way", recorded by the Communards in 1986 and "If You Don't Know Me By Now", covered by Simply Red in 1989). But since you didn't write them, you gain nothing from this revival, and struggle along on the cabaret circuit.

Finally, in 1995, you are booked to play the Cafe Royal ("London's premier air-conditioned night spot", according to the master of ceremonies who introduces you). And when you step out on to the Cafe's CD-cover sized stage, you notice there are only 27 paying customers in the audience, including a Russian man abandoned after his wife walked out on him during dinner. Now would you not, in those circumstances, look a little bitter? By what must have been a supreme effort of will, Harold Melvin does not look remotely unhappy. He smiles, he flirts with a couple of elderly ladies sitting at the front table, he tells us how thrilled he is to play for us. And though he has probably said this every single night of his near 40-year career, the manner he says it in, makes you sort of believe him.

What Harold can't do, however, is dance like he used to. Those syncopated shimmies and soft-shoe routines have been slowed by time and illness. He moves in an odd, stacatto way, as if forcing his extremities into action. His singing, too, is slurred and slurried. And when he comes to introduce his songs with a little history, at times he mumbles so badly you think it is Bob Dylan up there. But you forgive him all that, because he has brought along Donnell Gillespie. The latest in a line of Pendergrass replacements, Gillespie may be no match for his predecessor in trouser behaviour, but his huge voice is equally capable of exciting the hairs on the back of the neck.

As he swings through all the big Blue Notes hits - "The Love I Lost", "Satisfaction Guaranteed", "Wake Up Everybody", plus the two that everyone else made money on - you notice, too, that your feet have started to move in an uncontrollable fashion. No more than an hour they play for - slick, crafty, beautifully modulated - after which Melvin says it was "a genuine, true and real privilege" to sing for us. You wonder what hyperbole he would reach for if faced with the audience Gillespie deserves.