POP / One night in the life of a DJ: It isn't easy being a jobbing DJ. Charlie Gillett reports from behind the turntables at one of London's most demanding clubs, the Mambo Inn

Every weekend for the last five years, hundreds of people have lined up around the block in a back street in Brixton, south London, to dance to music they may never have heard before. The whole concept goes against all known formulas for successful dance clubs in London, where a tyranny of style invariably dictates what kind of music is 'allowed'. Mostly, it's a simple matter of musical generations, and woe betide the DJ who tries to cross the fault lines; the more recent the music, the more strict the divisions. But because the audience at the Mambo Inn is such a mixture of ages and nationalities, none of this matters. They go in a spirit of adventure, to find DJs who play records from Africa, South America and the Caribbean as well as non-mainstream American-based music. Virtually any record can be made to 'work' at the Mambo - if the DJ leads up to it with the right combination.

There's a big difference between playing records on the radio and at a dance club, and most of my experience is from radio. A radio listener can switch off, and the DJ never knows; but play the wrong record at a club and your audience reaction is all too visible - the dancers stop and look at you: what are you playing this for? You have the choice; to tough it out, or admit defeat and fade it. Either way, it's horrible.

The three resident Mambo DJs - Gerry Lyseight, Max Reinhardt and Rita Ray invite a guest DJ to vary the menu every week. Tonight's my night, taking over from Max at 11pm in the upstairs room with the crowd still coming in, queuing at the cloakroom, ordering drinks, comparing atmospheres upstairs and down. Starting with an easy groove, I kick off with some old Jamaican records - a ska version of 'Watermelon Man' by Baba Brooks, and Marcia Griffiths' rock-steady classic, 'Feel Like Jumping'.

It takes a little while to get acclimatised. The room has a high ceiling, and it's tricky getting the level right. If the volume's too high, it bounces off the wall; too quiet, and there's no impact. After four Jamaican records, I switch to a sequence from Southern Africa, starting with track 15 on the Dark City Sisters CD. But in the gloom I confuse channels on the mixing desk, and the room is suspended in silence until I find the right one: finally the last part of the guitar intro hits the speakers, but by then I've brought the dancers to a shuddering halt.

The room has suddenly become uncomfortably hot, and I'm glad to hide my sweaty face behind the turntable rack. I look up again when Dorothy Masuka's 'Kathini Zulu' is safely up and running. Normally it's a never-fail floor- filler, but tonight it doesn't seem to be having the contagious effect I was depending on. Then I realise why: on both turntables the green lights are off - the warning sign that they are not running at true speed. In order to make the breakneck tempo of his soukous records easier early in the evening, Max had slowed them down, and I had forgotten to reset them. So far, I've been playing every record slow.

For club DJs, there's craft and there's art: the craft is to create a seamless stream of sound, blending rhythms and tempos; the art is to make a change which they may notice but still accept, because it's done with casual authority. Tonight, file me under clumsy.

Max tells me I've got 10 minutes left of my first set, and I end with two stand-bys from the early Eighties, the Kenyan anthem 'Shauri Yako' by Orchestra Super Mazembe; and 'Ami- O' by the Cameroonian Bebe Manga. There's satisfaction in leaving Max with a room packed with heaving bodies.

Downstairs, the floor is chock-a-block: all I have to do is keep it like that. I resist the temptation to start with the same winning sequence I used at the Mambo last time - Bally Sagoo, Khaled and Robert Palmer's 'Sneaking Sally through the Alley' - and kick off with the Mar- Keys' 'Last Night'. It grooves like I knew it would: we're off on a different trip.

But the train stops sooner than I intended. Humphrey Lyttelton's 'Bad Penny Blues' is driven by Johnny Parker's brilliant boogie piano and pushed by Humph's rhythmic phrasing on trumpet. But although its eight-beats-to- the-bar might have carried on from the Mar- Keys' boogie bass-line, 'Bad Penny Blues' doesn't have an equivalent snare pattern; while half of the dancers valiantly try to find its pulse, the other half give up, taking the chance to get a drink or take rest. I've lost the momentum, and it could take a while to recover . . .

It does. Jah Wobble's 'Amor' should be a Mambo natural - a hybrid of reggae feel and Spanish lyrics; but although it holds the people who are there, it doesn't bring any exiles back to the floor. It's getting hot again, when Salt 'n' Pepa come to my rescue. Their current album Very Necessary is irresistible from start to finish, and 'Shoop' does the trick; within 20 seconds, the room is rocking from end-to-end. 'Shoop's' chorus of 'shoop-shooby-doop' sounds a lot like the chant in the 30-year-old 'I'm Blue' by the Ikettes, which is all the excuse I need to play it; its presence is awesome - how did they get everything so loud in those days?

Aware of Gerry sitting near me, I'm disappointed with how uneven the set feels. He leans over to point at the overload meter on the desk - 'I think you're a bit loud.' I've always been annoyed with sound engineers who confuse volume with excitement, and here I am doing the same thing. Chastened, I drag the faders down.

I'm into an R & B thing now, and can't get out of it until I've played King Floyd's 'Groove Me'. When this came out in 1971, I thought it was the sexiest record I'd ever heard. Less than three minutes (no disco mixes in those days), it always brings people together at the Mambo. I look out at the crowd - a circle of women make up moves to go with the beat, their faces lit with laughter; black-and-white couples, newly met, oblivious to everything except each other.

After five R & B records in a row, and with 10 minutes left, I go back to the tropics. Nyboma's 'Papa Sodolo', another seminal African record from the early Eighties, hits the spot and keeps people on the floor. I finish with track 11 on the compilation Jive Soweto, a near-rap sung in Zulu with a bass-line that threatens the building's foundations. It works; they stay; I leave. As I pass a dancer on my way out, she smiles. 'Great set, Charlie.' Forgiving, those Mambo dancers.

The Mambo Inn, every Fri and Sat, 9pm to 2am, at the Loughborough, Brixton, London SW9

Photograph of Charlie Gillett by Laurie Lewis

(Photograph omitted)